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Sexual Reproduction: Definition, Advantages, and Examples
Continue ReadingWhat is Sexual Reproduction?
Sexual reproduction involves the fusion of haploid gametes. It is defined as a mode of reproduction in which a diploid zygote is formed after the fusion of the male and female haploid gametes. Later, the zygote is developed into a new offspring that is not identical to the parent organisms.
Sexual reproduction differs from asexual reproduction where an organism can reproduce without fertilization. Therefore the offspring is a clone of its parents. In the case of sexual reproduction, fertilization is a must for zygote formation and the offspring develops with distinct genetic characters. Sexual reproduction can be divided into two types- Syngamy and conjugation
Sexual Reproduction Definition
A process of producing individual offspring by parents is called reproduction. It is the crucial process for the survival of all living organisms, they increase their number by reproducing by different means. Sexual reproduction is also a type of reproduction where two parents are involved. In this process, a fusion of two haploid gametes results in a diploid organism.
Sexual Reproduction Etymology
The word reproduction is made up of two Latin words, re meaning “again” and production meaning “to produce”.The word sexual is derived from the Latin word sexualis, meaning “copulation or generation”. Sexual reproduction is also called syngenesis.
Sexual Reproduction and Asexual Reproduction
The process of reproduction is divided into two types-
Sexual reproduction and Asexual reproduction.
Sexual Reproduction includes gametogenesis and fertilization that results in a diploid zygote formation. The incorporation of cell division is called gametogenesis. It starts with mitotic division then the daughter cells undergo reduction division (meiosis) to produce haploid gametes. The female carries haploid eggs whereas the male carries haploid sperm cells. After the sexual intercourse, the sperm cell comes closer to the egg cell resides in the ovum of the female for the union. The process proceeds with the combination of the genetic material of sperm and egg, which is called fertilization. The diploid zygote then undergoes mitotic divisions to form an embryo.
Asexual Reproduction has some differences as compared to sexual reproduction. It does not require two parents and also does not undergo the process of fertilization. The process of meiosis is also not present. The individual produces an offspring that is genetically identical to its parent.
Types of Sexual Reproduction
Sexual reproduction is divided into two types that are syngamy and conjugation. The fusion of haploid sex cells that results in the formation of the diploid zygote is called syngamy. It is a synonym for fertilization. It is a common type of reproduction adopted by higher plants and animals.
Conjugation includes the process of coming together of two organisms in a temporary fusion. The fusion completes by a cytoplasmic bridge. It is adopted by microorganisms or single-celled organisms such as bacteria, protozoans, etc.
Sexual Reproduction in Single Celled Organism
Various single-celled organisms such as bacteria and protozoans reproduce sexually by the method of conjugation. Conjugation is the process where two bacterial cells transfer their genetic material by a plasmid. In the bacterial cell, the plasmid is a part of the chromosome.
Bacteria also use conjugation to acquire a beneficial gene for survival. Conjugation is also used by some protozoans in which two protozoan cells come together to transfer their genetic material. After separation, each of the cells becomes a fertilized cell. Conjugation is also seen in some algae and fungi species.
Viruses also show some evidence to reproduce sexually by genetic recombination method, but sexual reproduction in viruses is not studied properly and is still contested.
Syngamy in Multicellular Organisms
The multicellular organisms including humans reduce sexually by syngamy. It completes in two steps- plasmogamy and karyogamy. Plasmogamy refers to the union of cytoplasms of two gametes. In the next step, the fusion of the nuclei of two gametes occurs which is called karyogamy. The union results in the formation of a diploid zygote. The zygote undergoes series of mitotic divisions to form an embryo. Syngamy is also classified into many types.
Plant Syngamy
The plant completes its life cycle in two generations, the gametophyte, and the sporophyte generation. The gametophyte generation starts with a haploid spore that produces a haploid gametophyte. Sex organs are present in the haploid gametophyte that participates in the fertilization process.
A diploid zygote is formed after fertilization. The zygote develops into a sporophyte from which sporophyte generation starts. It produces spores in a specific organ called sporangium. Higher plants bear the sex organ called flower that can be unisexual or bisexual.
The pistil is a female organ and anther is a male reproductive organ in plants. The pollen grains are present in another that bears sperm cells. The ovary is located in the pistil that has egg cells in the ovule.
The transfer of pollen grains to the ovule is called pollination. Pollination can occur by different means such as self-pollination, cross-pollination. It results in the formation of a diploid zygote. Later the zygote develops into an embryo and endosperm from a nutritive tissue called a seed.
Animal Syngamy
Most of the animals are unisexual and reproduce by mating with another organism. They display sexual dimorphism, sexual selection, and courtship rituals. The occurrence of two sexually distinct forms of an organism is referred to as sexual dimorphism. For example, male birds have more attractive features than female birds.
Human Syngamy
Humans can reproduce naturally by sexual means only. The process includes several courtship rituals, copulation, pregnancy, childbirth, and parental care. The internal fertilization takes place after intercourse which results in a diploid zygote.
The zygote undergoes mitosis and forms an embryo. The embryo develops into a fetus that receives nutrients from an umbilical cord. The pregnancy period or gestation period is of 9 months or almost 266 days. Childbirth is followed by parental care.
Advantages of Sexual Reproduction
There are several advantages of sexual reproduction. The number of chromosomes remains across generations. For example- humans have 46 chromosomes half comes from each of the parents, before fertilization the haploid gametes are formed by meiosis. Therefore after fertilization, they keep the number of chromosomes like the somatic cells. Sexual reproduction also improves the gene pool. It performs syngamy thus helping to maintain genetic diversity.
Sexual Reproduction Citations
- Exceptionalism is not exceptional in relation to sexual and reproduction mechanisms: Contrasts of human and animal sexuality. Clin Anat . 2017 Oct;30(7):940-945.
- The separation of sexual activity and reproduction in human social evolution. Adv Exp Med Biol . 2014;814:159-67.
- Endocrinology of human female sexuality, mating, and reproductive behavior. Horm Behav . 2017 May;91:19-35.
- The State of Adolescent Sexual and Reproductive Health. J Adolesc Health . 2019 Dec;65(6S):S3-S15.
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Animal Cell: Definition, Diagram, Structure, and Function
Continue ReadingWhat is Animal Cell?
The cell is the structural and functional unit for all organisms. Based on the organisms, a cell is divided into two types named as Plant cell and animal cell. All the animals have a functional unit called a cell. It also acts as a basic unit for reproduction.
After the invention of the microscope, animal cells were first observed in the 17th century. The cell was first discovered by an English natural philosopher, Robert Hooke. A Dutch scientist named Anton van Leeuwenhoek observe these cells under the microscope and described bacterial cells and red blood cells of animals.
Animal Cell Definition
A basic structural and functional unit of all animals, animal tissues, and organs is called a cell. They are eukaryotic cells that consist of a well-defined nucleus and membrane-bound cytoplasmic organelle. Both animal cells and plant cells are eukaryotic structures but the plant cell differs in the presence of a cell wall. Apart from this, plastids, vacuoles are also absent in animal cells, and they cannot perform photosynthesis.
Animal Cell Structure
An animal cell is made up of some cellular organelles name as, cytoplasmic structures, cytosol, and cell membrane. The cytoplasmic organelles remain embedded in the cytoplasm and each of them has a distinct role in the proper functioning of the cell. The fluid-like substance inside the plasma membrane is called cytosol, which is the site for a wide variety of cellular processes, e.g. Cell division
Animal Cell Labelled Diagram
Cell Membrane
It is the outermost membrane of an animal cell. The cell membrane is made up of a lipid bilayer with embedded proteins and carbohydrates. It is selectively permeable which means it allows only selective substances to enter into the cell. Molecules with small molecular weight can easily cross the membrane whereas ionic and large molecules are transported with the help of transport proteins. The main function of the cell membrane is to provide structural integrity and support to the cell.
Nucleus
The nucleus is considered the most prominent cellular organelle. It is mainly located at the center of the cell and is composed of the nuclear membrane, nuclear bodies, nucleosol, and chromosomes. The nuclear membrane surrounds the nucleus and is also called the nuclear envelope that consists of nuclear pores. The genetic material is also found in the nucleus, therefore it regulates most of the cellular activities and is considered as the control center.
Endoplasmic Reticulum
The network of flattened sacs or tubules is called the endoplasmic reticulum. They are divided into two types, RER and SER. The rough endoplasmic reticulum has ribosomes studded in membrane whereas smooth endoplasmic membranes do not contain ribosomes. The endoplasmic reticulum has the main function of protein synthesis, lipid synthesis, and protein modification.
Golgi Apparatus
Golgi apparatus is a membrane-bound organelle comprised of stacks of cisternae. The main function of the Golgi apparatus is the packaging and secretion of biomolecules. Golgi apparatus is found in the cell in a collective form which is called Golgi complex.
Mitochondria
Mitochondria are called the “powerhouse of the cell”. It is also a double membrane-bound organelle. Mitochondria has its DNA which is called mtDNA. It involves ATP synthesis, glucose, and fat metabolism.
Lysosome
A single membrane-bound organelle that contains various digestive enzymes is called a lysosome. The main function of the lysosome is the digestion of intra and extracellular waste material.
Endosome
Endosomes are also called vesicles. They are single membrane-bound organelle that has the main function of transport.
Vacuole
Vacuoles are storage organs. They are only present in animal cells and absent in plant cells. The functions of vacuoles include osmoregulation, storage, and secretion.
Cytoskeleton
The skeletal frame or internal network present in the cell is called the cytoskeleton. There are three types of cytoskeleton named actin filaments, intermediate filaments, and microtubules. The cytoskeleton has the main function of controlling cell shape and cell movement. It also involves the formation of specialized structures like cilia and flagella in bacteria.
Types of Animal Cell
The animal cells are eukaryotic. Most animals are multicellular organisms that are made up of several cells. The animal cell is divided into different types.
Examples- skin cells, muscle cells, blood cells, nerve cells, sex cells, and stem cells.
The epithelial tissue or skin is made of skin cells. Tissue is a group of cells that perform a specific function. Blood cells are also categorized into red blood cells and white blood cells.
The nervous system in higher animals is made up of specific cells called nerve cells or neurons. Sex cells are involved in sexual reproduction.
Animal Cell Facts
• The cell can be divided during cell division and form a cleavage furrow.
• The animal cells need oxygen for the citric acid cycle and aerobic respiration.
• The red blood cells and do not have a nucleus.
• They also lack plastids and vacuoles.
Animal Cell Citations
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Ecosystem: Definition, Types, and Examples
Continue ReadingEcosystem Definition
The word ecosystem originated in 1930 from a greek word, where oikos means house and sustema means organized body. The system comprising of biotic and abiotic components is called as an ecosystem. Both these components work together in unison to complete an ecosystem. All the living things are said to be biotic, whereas the non-living things are said to be abiotic.
Ecosystem can be thought of as the habitat where different organism reside in unison in the habitat. As cell is the fundamental unit of life, ecosystem is also a fundamental unit providing habitat. In simple words ecosystem can be defined as the people residing in the environment. Thus, environment and organism constitutes the ecosystem.
Ecosystem Structure
Ecosystem comprises of two components and they are:
a) Biotic Component: They consist of producers, decomposer, consumers, herbivores, carnivores and omnivores.
b) Abiotic Component: It consist of soil, water, sunlight and air.
a) Biotic Component
All living things are included in the biotic components. Living things can further be characterized into prokaryotes and eukaryotes. Prokaryotes lack nucleus instead have a nucleoid region whereas the eukaryotes possess nucleus along with various other organelles such as mitochondria and chloroplast.
Example of prokaryotes are eubacteria and archaea, whereas eukaryotes example are fungi, algae, plants, protist and others.
In order to prepare food plants, have chlorophyll, thus they can be called by the name producers. Those that feed on feed on producers are called as primary consumers who in turn are the food source for higher consumer levels such as secondary and tertiary.
Example of consumers are animals.
Herbivores are said to be those that feed on plants. Carnivores are the one’s that feed on animals. When herbivores and carnivores are compiled, a term called as omnivore comes out and are those that feed on plants as well as animals.
b) Abiotic Component
Soil, water, air, sunlight, minerals and rock constitute the abiotic component. All these components of abiotic plays a role in ecology.
For example, these compounds could provide nutrition source which is the requirement of many organism for their growth. Other functions are to provide a habitat to reside.
Ecosystem Interaction
Through the nutrient cycles and flow of energy, biotic and abiotic components, are connected and work together as one system. Via photoautotrophs nutrients enter the ecosystem and they are plants and green algae that carry out photosynthesis.
Organism that feed on photoautotrophs are called as heterotrophs. Thus, as we can notice it’s a complete flow of cycle from one organism to the other and as these organism die, they are termed as decomposers and the process is called decomposition. With the decomposition process nutrients reach back to the environment where they are re-used and thus, the cycle continues to proceed.
An example of biotic is Predation, with the increase in the number of predators the number of prey would significantly decrease. Thus, predation increases prey decreases but if other organism except the predators are also dependent on the prey, then it could result in an imbalance to those species.
In abiotic, they can control the population and the number of species. For example, acid rain is usually precipitation of hydrogen ions which is harmful to plants, soil and animals which cannot tolerate low pH. Temperature, salinity, light are other factors of abiotic component.
Types of Ecosystem
There are 4 types of ecosystem and they are:
a) Terrestrial Ecosystem
Terrestrial means land thus, the ecosystem present on land is called as terrestrial ecosystem. Forest ecosystem, dessert ecosystem, tundra ecosystem and grassland ecosystem are some of the examples. Forest system would contain various trees, plants, along with animals.
Plants would become the producers, providing wood and fruits. They also have various other roles such as maintaining the temperature, carbon content and etc. Tropical and temperate climate are most favorable for grasslands. As the area consist of only grass, thus, only grazing animals would be found at such locations.
Example of grazing animals are cattle’s, deer, goats and others. In tundra ecosystem, the area is covered with snow and no trees are seen. In summer and springs the snow is seen melting forming ponds and lakes and flowers blossom.
Lichens are also seen. Tundra ecosystem also has functions such as maintaining the temperature and serving as a water source. The climate in dessert ecosystem is dry and windy. The deserts will contain plants such as cactus, animals such as camels, birds, insects and reptiles.
There are also sand dunes and rocks seen in desert. Desert ecosystems organism have made quite adaptations due to extreme arid conditions, such as camels store water in their body is a type of an adaptation to survive in the particular environment.
b) Freshwater Ecosystem
These are the water bodies ecosystem but not the salty one’s. Such ecosystem inhabit fishes, reptiles, plants, insects, algae, fungi and others. Fresh water ecosystem is of further two types lotic and lentic ecosystem. Lentic means still. Thus, it means the ecosystem with still water. Example are ponds, lakes and puddles.
However, in lakes, various zones are formed such as littoral, limnetic and profundal. The sea shore part of water is called as littoral. Large amount of light can pass through it. The layer beneath the littoral is the limnetic zone where light cannot pass completely. The part where there is complete darkness in limnetic zone is called as benthic zone whereas the zone where little light can penetrate is called as photic zone.
The plants found in these zone vary depending on the plant’s requirement. Lotic means freely flowing. Example of lotic ecosystem is streams and river. Thus, with the moving water force, plants and animals in this ecosystem have adapted themselves.
c) Marine Ecosystem
In this type of ecosystem, the water is supposed to be salty. Example of marine ecosystem are seas and ocean. One of the most abundant ecosystem is the marine ecosystem. Due to large population of algae, marine ecosystem releases huge amount of oxygen which is available to us.
d) Artificial Ecosystem
As the name itself suggests, it is man-made which can be a terrestrial, freshwater or marine ecosystem. Terrarium is a man-made ecosystem. Artificial ecosystems are made for research purpose, conservation and for ecology.
Ecosystem Process
Two process simultaneously occurs in an ecosystem, which are connected to each other and they are the flow of energy and recycling of the material that is left behind. During this process, some energy is stored in the form of ATP while the other is released out in the form of heat. However, as the planet is open, thus, heat cannot be trapped.
i. Energy Flow
In energy flow, productivity is the term which determine the amount of biomass produced in a particular ecosystem. The units of productivity are grams per square meter per day.
Productivity is of two types; primary productivity refers to plants productivity whereas secondary productivity refers to animals. Primary production starts from starts from the green plants such as algae and other plants, which undergo photosynthesis and are the first producers as the flow of energy starts from them.
Chloroplasts traps the energy from the sun which contains chlorophyll, which converts light energy into various energy sources such as sugar. However, animals do not have any organelle as such and thus depend on heterotrophs. Thus, with the photosynthesis plants can prepare their own food using sun and a few inorganic sources.
These energy reserves made by plant are stored which can be later used by other organism who cannot prepare their own food. Thus, in this manner the flow of energy continues to happen from producers to consumers and then to primary and secondary consumers and so on and finally to the tertiary consumers.
Finally, that is followed by decomposers which takes up all the fallen material and gets reused. Thus, the energy flows in this manner.
ii. Biogeochemical or Nutrient Cycling
Through various modes, phosphorous, carbon, nitrogen can enter the chain. For instance, plants taking up such elements from their roots which are present in the soil. In animals it could enter when they eat their prey, which might have these elements present in the nearby vicinity.
The decomposed food which is fallen might start release these elements and could reach the living organism. In terms of decomposition, it could be said that everything fallen off gets reused, thus, planet here could be counted as a closed plants as there is continuous flow of energy.
iii. Community Dynamics
As ecosystem consist of various things which makes it complete, thus they can be called as dynamic. However, a natural disaster could change the dynamics such as volcanic eruption which would result in a bare land, where various species will again start to reside. However, the very first residents are said to be lichens, which will make the place more residable for others.
Succession happens when the position of one dominant species is taken by the other species or its group. This will continue to happen until a balance has been achieved and until any natural calamity has taken place which will again repeat the same cycle, where again colonization of new land is called as primary succession and recolonizing in the same place is called as secondary succession.
iv. Function and Biodiversity
Ensuring the flow of energy and nutrient cycling from abiotic which is sun to biotic factor is the function of an ecosystem. To maintain homeostasis, physical, chemical and biological system work together in unison. Within biodiversity comes the biotic factors.
Ecosystem is said to be healthy when, there is more diversity in biotic components. Thus, the chances of ecosystem will flourish when there is biodiversity within species, thus, improving stability and productivity of the ecosystem.
Ecosystem Examples
i. Deciduous Forest Ecosystem
In deciduous forest, huge number of trees are seen, whose leaves fall off during the season and start to regrow during the season approaching. Falling of leaves is an adaptation made by the plant to protect itself from the cold.
The types of trees seen are maples, oaks, elms, basswoods, beeches, birches and other. The trees found in southern hemisphere is southern beeches. Frogs, salamander, turtles, birds, insect, rabbit, slug, spiders, mice, chipmunks are the various animals found.
ii. Savannah Ecosystem
They are a combination of grassland and woodland. The trees in this ecosystem are quite spread out thus, allowing light to reach the ground. Thus, small plants grow quite well. Thus, a lot of grazing animals are seen in this ecosystem such as cattle’s, goats and sheep.it is said to be an ecosystem in-between the forest, grassland and desert.
iii. Coral Reef Ecosystem
This ecosystem consist of coral reef which are coral polyp’s colonies. Corals always lives in groups and are hard. This is considered to one of most spread out ecosystem because of the diversity. Coral reefs are known by the name rainforest of the sea. They reside in shallow waters. Other organism found with corals are sponges, fish, mollusc, worms, tunicates and echinoderms.
iv. Hot Spring Ecosystem
In a hot spring ecosystem, the water from the spring gets heated geothermally i.e the earths mantle causes the water to heat and the spring water has higher temperature than the nearby vicinity. In such types of ecosystem specific type of organism would only be found such as thermophiles. Thermophiles are those that can survive in extreme heat. The temperature ranges from 45-80℃. The type of species found are thermophilic bacteria ex Legionella, archaea and thermophilic amoeba ex Naegleria fowleri.
v. Micro-Ecosystem
Microsystems are said to be those which are formed in confined spaces but some environmental factors have to be taken care of are called as micro-ecosystem. Ex with a tree a lot of different species live with it such as lichens, insects, plants and other animals. The plants on them itself provide a place to reside for the other animals.
Ecosystem Citations
- Scaling-up biodiversity-ecosystem functioning research. Ecol Lett . 2020 Apr;23(4):757-776.
- A guide to ecosystem models and their environmental applications. Nat Ecol Evol . 2020 Nov;4(11):1459-1471.
- When Do Ecosystem Services Depend on Rare Species? Trends Ecol Evol . 2019 Aug;34(8):746-758.
- Springs ecosystem classification. Ecol Appl . 2021 Jan;31(1):e2218.
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What is Biosphere? Definition, Component, and Examples
Continue ReadingWhat is Biosphere?
The biosphere is the area of the planet where living things flourish and live. It is the area of the planet that is capable of supporting life. The atmosphere, lithosphere, and hydrosphere are the three other spheres that make up the Earth. However, not all of them are home to live creatures. The biosphere is the collection of parts or places where life can be located. As a result, the biosphere may alternatively be defined as the total of all ecosystems on Earth.
The word “biosphere” comes from the Greek words “bios” (life) and “sphaira” (the form of the Earth). Eduard Suess, an English-Austrian physicist, used the term in his four-volume work “The Face of the Earth.” He discussed the relationships between living things as they are sustained by the Earth in this book.
Biosphere Definition
The word “biosphere” refers to all of the Earth’s ecosystems. As a result, it encompasses both non-living (such as sunlight and water) and living creatures.
The term “biosphere” refers to the areas or regions of the Earth that are home to life. It is one of the characteristics that distinguishes the Earth from the other planets.
The biosphere, atmosphere, lithosphere (geosphere), and hydrosphere are the four spheres that make up the Earth. The biosphere is the portion of the Earth that contains all living populations as well as their surroundings. It is a component of the earth that supports life. The gaseous component of the Earth’s atmosphere surrounds the lithosphere.
The lithosphere, on the other hand, is made up of the crust and upper mantle of the Earth. In other sources, the land or terrestrial portion is referred to as the geosphere, which, unlike the lithosphere, contains the core, in addition to the crust and mantle.
All of the water on the Earth’s surface is referred to as the hydrosphere. Some sources use the word interchangeably with the ecosphere, which, properly speaking, refers to all of these spheres interacting in a closed system.
The biosphere is the part of the planet where living things exist (biology definition). All living creatures in the lithosphere, atmosphere, and hydrosphere are included. Artificial biospheres, such as Biosphere 2, which is by far the biggest closed environmental system ever constructed by mankind, are also available for research and inquiry. Bios-, which means life + sphere, is the etymology.
Origin and Evolution of Biosphere
Early prokaryotes flourished in a biosphere deprived of oxygen around 3.8 billion years ago. Some of these creatures eventually developed to be able to use light, water, and carbon dioxide to produce chemical energy-rich compounds while also creating oxygen molecules as a byproduct.
The method of producing food using light energy is now known as photosynthesis, and the creatures that can do it are known as autotrophs. As a result, more species, ranging from single-celled algae to multicellular autotrophs like vascular plants, were able to consume carbon dioxide in the atmosphere and eventually give oxygen to the environment. As the amount of oxygen in the atmosphere evolved, so did the diversity of aerobic creatures that lived and developed.
This permits more sophisticated life forms, such as vascular plants, animals, and humans, to thrive in the presence of oxygen. To answer the question, “How is biodiversity connected to the biosphere?”, the answer is straightforward. It resulted in a “healthy” environment teeming with various species. When we say “healthy,” we imply that different groups are able to fill distinct ecological niches.
Autotrophs are the food chain’s producers. Heterotrophs play the function of natural biological controls since they are unable to generate food in the same manner that autotrophs can, and so must devour other species.
Herbivores are heterotrophic organisms that only eat plants. Those who consume only animal flesh are known as carnivores, whereas those who eat both plants and animal meat are known as omnivores.
Decomposers are another significant ecological niche. These organisms breakdown deceased creatures or decaying tissues, as well as turning organic materials into simpler chemicals or molecules that feed the Earth. Fungi, for example, degrade dead plants and animal matter. They decompose the cells of deceased plants and animals into simpler compounds, which the environment may use as organic nutrients.
Biosphere Components
The lithosphere, atmosphere, and hydrosphere are the three components that make up the biosphere. However, not all of them are flourishing or inhabited by live creatures. Only the regions of the biosphere where life may be discovered and supported are considered to be part of the biosphere. The biosphere includes, for example, the area of the sky where birds may be observed flying. Higher up in the atmosphere, however, where life can not survive, is not considered part of the biosphere.
I. Abiotic Component
The following is a description of these three abiotic biosphere components:
a) Lithosphere
The biosphere’s terrestrial component is known as the lithosphere. It has solid landmasses such as our continents and islands, for example.
The lower mantle and core of the planet do not support life and so are not a part of the biosphere. Apart from this, all of the other components support life, from the tiniest bacteria to huge animals and lofty trees, by providing shelter and food.
b) Atmosphere
The gaseous blanket that covers the Earth is known as the atmosphere. It contains various gases like carbon dioxide, oxygen, and other gases that aid in the survival of living creatures such as plants, animals, and people.
The upper atmosphere, on the other hand, has a low oxygen content, which is why flying birds may be found under the Earth’s surface at a depth of 200 metres. Apart from supplying gases for respiration, the biosphere’s atmosphere performs a special function in shielding living creatures from the sun’s damaging UV radiation.
c) Hydrosphere
All of the Earth’s water is referred to as the hydrosphere. As a result, it is also known as the aquatic region. It does, however, contain solid forms like glaciers. The hydrosphere, which sustains life, plays a critical role in controlling the Earth’s temperature. It also provides the water that all living creatures require.
II. Biotic Component
Plants, animals, and microbes are among the biotic components. These biological components are also the foundation of the ecosystem’s food chain.
a) Plants
The major producers are plants. Photosynthesis is how they get their nourishment. They are sometimes referred to as autotrophs. They also participate in garbage recycling. They are, nevertheless, the only source of food for all living organisms, including animals and humans.
b) Animals
These are the ones who receive everything. They are unable to obtain their nourishment from non-organic sources. They rely on other sources, such as plants or tiny animals. Heterotrophs are another name for them. They utilise the food they eat to release energy and store it for later use. energy is used for development and growth.
c) Microorganisms
Microorganisms play an important role in the environment. Fungi, algae, bacteria, viruses, and other microorganisms are among them. They also act as decomposers, reducing the quantity of waste or dead materials. This decomposition process serves as a food source for them.
Organizational Structure of Biosphere
The biosphere is primarily defined as the total of all life and living creatures on the planet. There are five layers to the organizational structure:
i. Biomes
Large sections of the biosphere are classified into biomes. Tundra, grassland, woods, deserts, and aquatic biomes are the five types of biomes identified by scientists. A wide variety of plants and animals live in rivers, lakes, seas, oceans, and other watery environments. Desserts, on the other hand, are the driest places on the planet, with the least amount of rain each year.
Grasslands cover the Earth’s green regions. It does, however, receive moderate rainfall, although not enough to support big trees. Forests are regions where big trees predominate. Tundras are large stretches of land in the Arctic that are devoid of trees and have a continuously frozen subsurface.
ii. Ecosystem
A biological community and the physical environment together constitute an ecosystem. As a result, it takes into account both biotic and abiotic variables. The physical environment and living things work together as a unit. Terrestrial, freshwater, marine, and artificial ecosystems are the four types of ecosystems.
The grassland ecosystem and the forest ecosystem are examples of terrestrial ecosystems, which occur on land. The lentic and lotic ecosystems are examples of the freshwater environment, which is an aquatic ecosystem. The seas and oceans are home to the marine environment, which is a saltwater ecosystem. An artificial environment, such as a terrarium, is a man-made system.
iii. The Community of Species
Different species make up the community since the biosphere is so diverse. These species thrive in environments with acceptable or ideal abiotic variables like temperature, pH, and nutrition. A biological community, on the other hand, is described as an assemblage of interacting organisms (of the same or distinct species) living in the same place at the same time.
iv. Population
Population refers to all individuals of a given species residing in a single environment. The population might range from a few hundred to tens of thousands of people. Overpopulation occurs when the population of a species exceeds the ecological niche’s carrying capacity.
A population drop, on the other hand, is when the population size decreases. A population bottleneck occurs when the population size is reduced for a brief period of time. An overabundance of people may result in a battle for survival. Species will compete for limited resources with each other. As a result, a variety of symbiotic partnerships have developed.
In a partnership, individuals who give and receive are said to be in a mutualism, whereas those who inflict or cause harm to other species are said to be in a parasitic or predatory symbiosis. This is also the point at which natural selection kicks in. Species with useful or helpful variants are “favoured,” and so have a better chance of thriving and reproducing than those with less favourable characteristics.
v. Organisms
Organisms are the biosphere’s living creatures. Possessing a cellular arrangement and system that allows for numerous life activities is one of the characteristics that sets them apart from non-living materials. A genetic material holds the code for all biological processes as well as reproduction inside the cell.
Eukaryotes and prokaryotes are both possible. Eukaryotes include people, plants, and animals, whereas prokaryotes include microorganisms. The presence of an endomembrane system and internal compartmentalization leading to the development of distinct organelles distinguishes them. Eukaryotes have certain characteristics, but prokaryotes do not.
Factors Affecting Biosphere
Living and non-living entities constantly change the biosphere that surrounds the Earth. The biosphere and the actions of the living creatures that make up the ecosystem are influenced by a variety of variables. The following three variables have varying effects on the biosphere:
• The Earth is Tilting: The tilting of the Earth has a significant impact on the biosphere. Because it causes one side of the Earth to become cooler over a period of time while the other remains warmer. Seasons are one of the physical elements that influence the sorts of organisms that thrive in a certain area.
• Natural Calamities: Natural catastrophes have the potential to have a massive and long-term influence on the ecosystem. Volcanic eruptions, earthquakes, floods, and other natural calamities damage the ecosystem. The environment is ruined by rock, water, lava, and other potential factors.
• A few Minor Details: Other minor variables, such as temperature change, water, soil erosion, or any other type of change, have an impact on the biosphere and disrupt the existence of many species.
Importance of Biosphere
• The biosphere is the link between living creatures’ healthy lives and their interactions. A little alteration in the biosphere can have a big influence on living species’ survival. The biosphere, on the other hand, is vital to all living things because of this link.
• Promote the survival of life on Earth. The biosphere’s primary purpose and significance is to promote life on Earth. All living creatures on the Earth maintain life on the surface by adapting to diverse environmental changes, suitable climatic conditions, and the supply of energy as food.
Biosphere Facts
There are several fascinating statistics and numbers about the ecosystem.
• Biopoiesis and biogenesis are processes that help the biosphere evolve. Biogenesis is the process of life emerging from living matter, whereas biopoiesis is the process of life evolving from non-living matter.
• The biosphere is believed to include 8.7 million distinct species, according to scientists. Approximately 2.2 million people live beneath water, whereas 6.5 million live on land.
• The biosphere’s true depth has yet to be determined. Some of the fish are said to reside beneath the depths of 8,300 metres.
• Biosphere 1 is the natural biosphere of the Earth. However, certain man-made biospheres, such as Biosphere 2 and Biosphere 3, were constructed solely for scientific research.
• The biosphere’s biggest component is the hydrosphere. It takes up 71% of the Earth’s surface.
• From the surface of the Earth to the depths of the ocean, the biosphere is estimated to be 21,500 metres.
Organic Matter
• The biosphere aids in the recycling of nutrients such as oxygen and nitrogen in order to keep life on Earth going.
• Food or raw materials should be provided. Because all living things require food to exist, the biosphere plays an essential role in supplying food to various animals and plants.
Biosphere Reserve
People’s activities and interactions with the environment or their habitats are critical to the biosphere’s survival and future. By raising or reducing oxygen or carbon dioxide in the atmosphere, for example, the biosphere and the lives of species may be harmed. Human activities such as forest fires, pollution, and other factors contribute to it.
Yangambi, in the Democratic Republic of Congo, was the site of the first biosphere. There are, however, 563 biosphere reserves across the world. Furthermore, scientists have discovered a new biosphere near the Ethiopian town of Yayu. They will also use such reserves for agricultural purposes.
The following are some examples of biosphere reserves:
1. Australia’s Gran Arenal
2. Spain’s Fuerteventura
3. UNESCO biosphere reserves
Biosphere Examples
Biosphere 1 refers to the earth’s natural biosphere. However, human curiosity has led to the creation of biosphere2, an artificial biosphere. In Oracle, Arizona, Biosphere 2 is regarded as the human-made laboratory. The project’s primary goal was to investigate various aspects and gather useful information. It was created between 1991 and 1994. In terms of construction, it resembles a big greenhouse. Various groups of individuals attempted to live and work under the facilities.
Biosphere 2 was meant to be a 100-year expedition, but it collapsed after only four years. However, over the last four years, the five biomes have been dispersed across the biosphere, posing problems for scientists, who have been forced to abandon their research.
Furthermore, it is still available for research and excursions. You may simply take a tour of the region and learn about the many elements and factors that make up the biosphere.
Biosphere Citations
- Reviewing Biosphere Reserves globally: effective conservation action or bureaucratic label? Biol Rev Camb Philos Soc . 2014 Feb;89(1):82-104.
- The Link Between the Ecology of the Prokaryotic Rare Biosphere and Its Biotechnological Potential. Front Microbiol . 2020 Feb 19;11:231.
- Transnational corporations and the challenge of biosphere stewardship. Nat Ecol Evol . 2019 Oct;3(10):1396-1403.
- Lignocellulose deconstruction in the biosphere. Curr Opin Chem Biol . 2017 Dec;41:61-70.
- The deep continental subsurface: the dark biosphere. Int Microbiol . 2018 Jun;21(1-2):3-14.
- Vanadium in Biosphere and Its Role in Biological Processes. Biol Trace Elem Res . 2018 Nov;186(1):52-67.
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Fragmentation: Definition, Mechanism, and Examples
Continue ReadingFragmentation Definition
Fragmentation can be defined as the process in which a larger fragment gets broken into smaller parts or chunks. It is an asexual form of reproduction which is seen processes such as DNA cloning and apoptosis. Fragmentation is seen happening in multicellular organism.
When a living organism gets broken into smaller pieces which are similar to the actual one is called as Fragmentation, in reproductive biology. Those broken parts are termed as fragments. The broken fragments again reassembles after its life cycle is completed and grows out as an adult that has the same shape, size and other characteristic similar to the parent.
What is Fragmentation?
The fragmentation process can happen due to natural as well as due to man made issues created. Example of fragmentation happening naturally is inappropriate climate conditions or stress from the outer environment can lead to fragmentation happening and those would further develop into adults that are identical to the parent.
Fragmentation can be seen in animals such as sponges, sea stars, worms, and plants such as fungi, lichens, molds and etc. A point to kept in mind that not the whole organism undergoes fragmentation but only a small part of it undergoes fragmentation to form a new organism.
Fragmentation Process
Fragmentation is also called as splitting as the organism loses its part which gets broken into smaller fragments and later after maturing forms and adult, identical to the parent cell.
What is Reproduction?
Reproduction can be defined as the process in which a new organism is formed from the parent organism. Reproduction can be of two types, sexual and asexual reproduction.
Sexual reproduction occurs when two parent mate to produce an offspring is called as sexual reproduction. The male gives the sperm whereas the females give the egg which gets fertilized and a zygote is formed which then matures to an embryo which will further form into an adult.
Some other types of sexual reproduction are allogamy, autogamy and external fertilization.
In asexual reproduction only one parent is responsible for the formation of an offspring. Examples are budding, binary fission, fragmentation and parthenogenesis. When a single bacterium is divided into two it is called as binary fission.
Formation of tiny organs within the parent’s body and after some time it separates out is called as budding. Examples are amoeba, paramecium, yeast and etc. parthenogenesis is seen occurring in fishes, amphibians and reptiles.
Fragmentation Steps
Fragmentation is an asexual mode of reproduction, where a part of the parent organism get detached and further grows into a matured adult, upon the completion of cycle.
Example are sponges, flatworm – planaria. During the fragmentation process organism’s body is splitted which forms the daughter cell.
Fragmentation and Regeneration
Fragmentation is when a part of the organism is detached from the parent, maturing into an adult. This is called as fragmentation. Regeneration is when the broken fragment tends to regrow the part which was lost. In fragment new organism is formed whereas new organs are formed in regeneration. Only few organisms have the ability to undergo fragmentation but regeneration is possible by all organism.
Fragmentation Advantage
a) Requires only a single parent.
b) The time taken by the juvenile to turn into a mature adult is quite less. Thus, less time consuming.
c) The number of offspring after fragmentation is quite huge.
d) Fragmentation can take place in varying climatic condition.
e) Maintains homeostasis.
Fragmentation Disadvantage
a) Since in fragmentation the offspring is formed from one parent, thus, the genes and the characteristics would also come from one parent which decreases the genetic biodiversity.
b) As the same traits have been passed on from various generation, thus the same disease genes will be inherited thus, increasing the extinction chances.
c) With less biodiversity, the chances to stand against the attackers and to survive would be minimal, thus, they might get extinct.
d) Large number of offspring from one parent.
Fragmentation Examples
a) Algae and Fungi: Usually fragmentation is majorly seen in lichens and fungi. Asexual fragmentation is seen in yeast, mushroom, smuts, molds and others. A special structure seen in fungi are the hyphae which are the branched structures and from them exist the mycelium. When hyphae are young, they procure food from the fungi. When it matures, it can reproduce and procure food on its own. Examples of algae that undergo fragmentation are Spirogyra.
b) Plants: Vegetative fragmentation is seen in plants. As plants produces new roots and new shoots, through the dispersion of stolon from ferns and perennial trees the colony diameter is increased. Thus, once the root is separated it grows on it own to form a new root system. The other examples are:
1. Woody Plants: Example are sheds, twigs and willows, which grows into a new plant. The shedding of twigs naturally is called as cladoptosis.
2. Detachment from the parent plant is also seen in non woody plants such as Kalanchoe daigremontiana. The plants fall off and occupy the ground where they form new plant.
3. Nonvascular plants examples are the liverworts, mosses which produce through fragmentation produces gemmae which fall off and become a new plant.
c) Animals: In animals it is seen in corals, which are hard and soft and can be fragmented. Examples are Euphyllia, Acropora, Caulstrea and Pocillopora. Other animals are sea anemone, starfish and nematodes.
Fragmentation Citations
- Plant reproductive susceptibility to habitat fragmentation: review and synthesis through a meta-analysis. Ecol Lett . 2006 Aug;9(8):968-80.
- The influence of habitat fragmentation on multiple plant-animal interactions and plant reproduction. Ecology . 2015 Oct;96(10):2669-78.
- Fragmentation modes and the evolution of life cycles. PLoS Comput Biol . 2017 Nov 22;13(11):e1005860.
- Sperm DNA Fragmentation: Consequences for Reproduction. Adv Exp Med Biol . 2019;1166:87-105.
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What is Hypertonic Solution? Definition, and Examples
Continue ReadingHypertonic Definition
The word hypertonic is a Greek word which can be broken into two words hyper means over and tonos means tension. Thus, from the two words it can be understood that hypertonic when there is too much of something, creating a tension. Thus, a solution is said to be hypertonic when it has high concentration of solute. Hypertonic could also be used when a solution is compared with other solution containing higher osmotic pressure than the other one.
Hypertonic Solution
A solution can be described as hypertonic if it persist higher level of tonicity when compared to the other solution present. Different solution will have difference in tonicities resulting in the movement of water through the membrane. An example could be blood which is hypertonic to a particular salt solution would push the water molecules towards the lower concentration i.e near the blood serum.
What is Hypertonic in Physiology?
In terms of tissue, a muscle could be characterized as hypertonic which has higher chances to tension as the length of the muscle’s changes. Thus, a hypotonic muscle will have less degree of tension when compared to the hypertonic muscle. A muscle will tend to show isotonicity when the tension on the muscle remains stable. This is said to be isotonicity.
Hypertonic Citations
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Mendel’s Law of Independent Assortment: Definition and...
Continue ReadingLaw of Independent Assortment Definition
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Mendel's Law of Inheritance
• Alleles are either dominant or recessive, according to the Law of Dominance and Uniformity, and a living creature with one or more dominant alleles will demonstrate the effect of this allele.
• The Law of Segregation states that throughout the creation of the gamete, each gene’s alleles segregate from one another, allowing the gamete to contain just one allele for each gene.
• The law of independent assortment is linked to the law of segregation, which says that during gamete production, segregation of various genes encoding distinct characteristics happens separately.
Mechanism of Independent Assortment
During gamete formation, the usual diploid number of chromosomes is decreased by half during meiotic division, resulting in haploid gametes with just 23 chromosomes. There are 46 chromosomes in a typical human diploid cell. Half of the chromosomes in a typical human diploid cell are derived maternally, from the female gamete (the egg cell or ovum), while the other half are derived paternally, from the male gamete (the sperm) (the sperm cell). Female and male gametes fuse together during sexual reproduction to form a new creature known as a diploid zygote.
“Different alleles and genes are separately acquired during the meiosis of sexually reproducing organisms,” according to the theory of independent assortment. The independent division of chromosomes into distinct gametes results in an independent assortment of chromosomes. Then there’s crossing over, which involves rearranging genes on each chromosome.
The Law of Independent Assortment describes how both parents’ genetic inheritance is random. During meiotic division, the two homologous chromosomes separate from one another, as stated in the Law of Segregation. As a result, both maternal and paternal gametes’ chromosomes are arranged separately; in other words, chromosomes present in one gamete do not always end up in the same source after division. As a consequence, one gamete may end up with all chromosomes from the maternal source, whereas another gamete may end up with chromosomes from both maternal and paternal origins.
Even while genes on the same chromosome or related genes are not randomly arranged, the crossing over that occurs during meiosis permits them to reorganise. The exchange of homologous chromosomal sections happens in both maternal and paternal chromosomes throughout this phase to guarantee the independent assortment of connected genes. As a result of the development of previously unknown gene mixes, various gene combinations produce a large amount of variation across individuals.
The resultant chromosomes are sorted randomly by combining the maternal and paternal chromosomes, according to Mendel’s law of independent assortment. Finally, the zygote contains a mixture of chromosomes rather than a distinct set of characteristics from each parent. As a result, chromosomes are thought to be independently arranged, resulting in a zygote with a mix of maternal and paternal chromosomes.
Because each gamete has 23 chromosomes and there are two gametes, the total number of potential combinations is 223, or 8,388,608. These many options provide for a lot of variation in progeny genes. The impact of gene variation on evolution and evolutionary processes is significant.
What is Law of Independent Assortment?
The process of random segregation and assortment of pairs of alleles during gamete creation leads to the generation of gametes with all conceivable combinations of alleles in equal quantities, according to one of the Mendelian Laws of Inheritance. In his study of garden peas, Gregor Mendel established the principles of heredity. He outlined numerous characteristics of heredity in his article detailing this study, which were codified as the Mendelian Laws after the rediscovery of Mendel’s work. The laws are Law of Segregation and the Law of Independent Assortment. The Law of Independent Assortment is manifested when two or more characteristics linked to distinct genes are inherited.
Principle of Independent Assortment
What does it mean to have an independent assortment?
The law of independent assortment states that the zygote inherits distinct characteristics from various alleles independently of one another. Where the random selection of one allele for one attribute is unrelated to the selection of another allele for a different trait in any way.
What is an independent assortment?
The term “independent assortment” refers to the fact that different genes are inherited independently of one another. The law of independent assortment calculates and assumes the combination of genes and their likelihood by multiplying the probabilities of each gene. Furthermore, the likelihood of having one gene has no bearing on the likelihood of having the other.
When does independent assortment happen during meiosis?
During metaphase I of meiotic division, eukaryotes undergo independent assortment in meiosis. It results in a gamete with mixed chromosomes. In a diploid somatic cell, gametes have half the number of normal chromosomes. Thus, gametes are haploid cells that may reproduce sexually by fusing two haploid gametes together to generate a diploid zygote with the entire set of chromosomes. The random distribution of chromosomes during metaphase with respect to other chromosomes provides the physical foundation.
Why is it necessary to have an independent assortment?
Independent assortment, in addition to crossing over, is responsible for the generation of new genetic combinations in the organism. As a result, it adds to eukaryote genetic diversity.
You must first grasp the rules of segregation in order to define an independent assortment. Separate gamete cells acquire two different, independently arranged genes during meiosis, according to the law of segregation. The maternal and paternal DNA, on the other hand, are randomly separated, allowing for more gene variety.
During the random partition of maternal and paternal DNA sources, the law of independent assortment is evident. The gamete may get maternal genes, paternal genes, or a combination of both due to random assortment. The genetic distribution is based on the random alignment of these chromosomes during the early stages of meiosis.
Law of Independent Assortment Examples
Gregor Mandel experimented with pea plants in a number of ways. As a consequence, he was able to figure out how heredity’s units, which are now known as genes thanks to the discovery of DNA and genetic information, function.
What causes independent assortment?
When alleles from at least two genes are randomly arranged into gametes, this is known as independent assortment. As a result, one gamete’s allele has no bearing on the alleles acquired by other gametes.
The transfer of various genes looked to be separate occurrences, according to Mendel. The chance of a specific combination of qualities in separate occurrences may be predicted by multiplying the individual probabilities of each attribute. The inheritance pattern of one characteristic will not impact the inheritance pattern of another in separate occurrences.
When Mendel mated round yellow pea plants with wrinkled green pea plants, all of the F1 peas had the dominant characteristics of round and yellow. He noticed round green and wrinkled yellow peas in the F2, as well as round yellow and wrinkled green peas.
Each dominant characteristic was found in 3/4 of the progeny, whereas each recessive trait was found in 1/4 of the progeny.
The four potential colour and shape combinations emerged in the ratio of 9:3:3:1, indicating that the genes for the two pairs of characteristics were randomly distributed into the gametes.
Independent events indicate that 3/4 x 3/4 = 9/16 will be both yellow and round if you have 3/4 yellow and 3/4 round. The proportions of the remaining three combinations may be determined in the same way.
Mendel observed 9 yellow rounds: 3 yellow wrinkles: 3 green round: 1 green wrinkled peas.
After the discovery of chromosomes and their activity during meiosis, it was feasible to explain the autonomous assortment as a result of each pair of homologous chromosomes moving independently during meiosis. It’s crucial to have a diverse set of genes in order to create novel genetic combinations that promote genetic diversity within a population.
Mendel’s breeding of pea plants with diverse features, such as garden pea plants that produce wrinkled green peas and another garden pea plant that produces rounder yellow peas, led to the discovery of the law of independent assortment. Because yellow and round characteristics were more prevalent, all of the first generation’s progeny were yellow and rounded peas. After mating the first generation with each other, the second generation exhibited significant variance. In yellow and green peas, the experiment demonstrated the separate inheritance of homologous characteristics on distinct alleles, since the generated offspring were not just yellow and round or green and wrinkled like their parents.
What is an independent assortment?
Let’s say you’re tracking two features in a random population of cats: eye colour (brown or green) and hair colour (white or grey). Brown eyes (B) are the dominant allele for eye colour, whereas green eyes (G) are the recessive allele (b). Let’s assume the white fur (W) allele is dominant over the grey fur (G) allele when it comes to fur colour (w).
At sexual maturity, heterozygous cats with dominant features, such as brown eyes and white fur, will generate gametes. If we follow the law of segregation, the alleles for eye colour will be sorted separately from the alleles for fur colour during gamete formation.
After meiosis, the resultant gamete will include random alleles, resulting in offspring with mixed characteristics if two heterozygous cats are crossed. For example, one of the kittens may have brown eyes (BB or Bb) and grey hair (ww). Another kitten could have grey hair and green eyes (bb) (ww). Others may have brown eyes and white fur as well (thus, possible genotypes could be BBWW, BBWw, BbWW, BbWw).
This is simply a hypothetical scenario. The eye and fur colour characteristics are polygenic in nature, which means that multiple alleles are involved in determining the offspring’s phenotype. The activity of chromosomes during meiosis and the random movement of each homologous pair of chromosomes during meiosis are currently used to explain the independent assortment.
Independent assortment is a critical step in the creation of novel genetic combinations that add to the genetic diversity of sexually reproducing people.
Law of Independent Assortment Citations
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Prokaryotic Cell: Definition, Examples, and Structure
Continue ReadingWhat are Prokaryotic Cells?
Microorganisms are broadly characterized as prokaryotes and eukaryotes, where both the classes differ from each other in their characteristic, structure, shape and the type of microorganisms they contain. Prokaryote is a Latin word, which when broken into two half means pro – before and kary– nut.
Thus, Prokaryotic cells can be defined as the one which do not contain nucleus and are devoid of various organelles as they lack internal membranes and thus their functioning isn’t that complex when compared to eukaryotes. As they lack nucleus, the genetic material is encapsulated in a region called the nucleoid.
Prokaryotic Cells
Prokaryotic cells lack organelles and organelles such as mitochondria, chloroplast and nucleus, they are said to be unicellular.
The DNA encapsulated in the nucleoid region of the cytoplasm is single stranded circular DNA, where the mode of reproduction is asexually through budding and binary fission.
In eukaryotes, sexual type of mode of reproduction is seen such as conjugation. Even if the prokaryote lack several organelles, it contains other structures and organelles.
Prokaryotic cells have a protein called Flagellin which is required for chemotaxis which will provide support to the bacteria. Other prokaryotic organelles are thylakoid systems, carboxysomes, ribosomes and magnetosomes.
The function of chlorosomes is to harvest light in green sulphur bacteria.
Carboxysomes as the name suggest fixes carbon content in bacteria. Magnetosomes are seen in magnetotactic bacteria. In photosynthetic bacteria, thylakoids could be seen. Example, cyanobacteria.
Very few prokaryotes contain a cell wall which is made up of peptidoglycan which determines the gram positive or gram negative of the bacteria depending on the thickness of the cell wall.
Thicker cell wall is found in gram positive bacteria whereas gram negative have an outer membrane along with a thin peptidoglycan layer. Archae lacks peptidoglycan layer and has pseudopeptidoglycan.
Prokaryotes vs Eukaryotes
The genetic material of prokaryotes is inside the nucleoid region of the cytoplasm whereas in eukaryotes its located within a double bound nucleus and the rest could also be found in the chloroplast and in the mitochondria if possessed. The energy source in both prokaryotes and eukaryotes is ATP and the genetic materials details are present in the genes for both.
The chromosome is circular for prokaryotes and linear for eukaryotes. As prokaryotes lack various organelles, they are smaller in size whereas eukaryotes are larger in size, thus prokaryotes have quick metabolic and growth rate.
Ribosomes are present in both eukaryotes and prokaryotes serving the function of protein synthesis; however, they differ in their subunit. The prokaryotic ribosome is 70S which has a larger sub unit of 50S and a smaller subunit of 30S. The eukaryotic ribosome is 80S, where the 60S is the larger one and 40S is the smaller one.
Bacteria, archae and cyanobacteria are the examples of prokaryotes whereas examples of eukaryotes are fungi, virus, protist and etc.
Examples of Prokaryotic Cells
a) Bacteria: Belonging to the domain eubacteria, bacteria are single celled and invisible without the aid of microscope. The DNA is encapsulated in the nucleoid region of the cytoplasm and these organisms lack compartments. The reproduction mode is asexually through budding or by releasing spores. These organisms can thrive in various conditions such as in extreme heat, extreme cold, soil, water, hot water springs, deep sea and etc. The types of bacteria could be cocci, bacilli, coccobacilli, spirilla, vibrio and etc.
b) Archaea: These organisms are also devoid of nucleus, of the domain Archaea and vary from eukaryotes and bacteria, however their genes quite replicate that of eukaryotes and possess various enzymes that are useful in transcription, translation and other pathways. These organisms can also survive in various conditions such as in salty climate, hot conditions, and in places where methane is been produced.
c) Cyanobacteria: Commonly known as the blue green bacteria or photosynthetic bacteria. They are derived from protists and are now place in a separate class of photosynthetic bacteria. They are found in soil, water and are economically very important as a large percent of oxygen we get is due to them. They have organelles such as carboxysomes, thylakoids and phycobilins which are the photosynthetic pigment, which gives them color. Examples include Nostocales, Pleurocapsales and Stigonoematales.
Prokaryotic Cells Citations
- Functional inclusions in prokaryotic cells. Int Rev Cytol . 1988;113:35-100.
- Macromolecule diffusion and confinement in prokaryotic cells. Curr Opin Biotechnol . 2011 Feb;22(1):117-26.
- How do prokaryotic cells cycle? Curr Biol . 2004 Sep 21;14(18):R768-70.
- Prokaryotic cells: structural organisation of the cytoskeleton and organelles. Mem Inst Oswaldo Cruz . 2012 May;107(3):283-93.
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Smooth Muscle: Definition, Characteristics, and Function
Continue ReadingSmooth Muscle Definition
It is a type of a muscle which is non-striated along with a nucleus centrally located and is not under our control, present in human body. Smooth muscles in human body have various roles. The shape of non-striated cells is spindle shape.
Smooth muscle is found stomach, blood-vessels, intestine and bladder. They are also found in the nervous system. Their functions are that help in digestion in gastrointestinal track. It removes toxins from the body, maintains electrolyte balance, blood pressure and oxygen content in tissues. In absence of smooth muscles this function would not take place.
Characteristic of Smooth Muscle
a) Single Nucleus: Smooth muscle being non-striated consist of a single nucleus located centrally in each of the cell. the activities outside and inside are controlled by the nucleus.
b) Shape of Smooth Muscle Cell: The shape of the smooth muscle is spindled shape, i.e filled in the middle and narrowed towards the end. Elasticity of smooth muscle is excellent. It can contract and expand very quick, which makes it suitable to be present in human body parts such as bladder, stomach and etc.
c) Filaments: If smooth muscle are observed under microscope, they appear like red line of smooth muscle which can travel from region to the other by cell membrane. The red filaments are actually actin filaments.
d) Contractility: Unlike the other muscles that can contract on their own, smooth muscle cannot be contracted on their own.
e) Elasticity: Smooth muscles are quite elastic and can stretch and return back to its original length.
f) Sarcomeres Absent: Sarcomere is like a bunch of filaments that has dark and white bands adjacent. However, this sarcomere is absent in skeletal muscle.
g) Tropomyosin Complex Absent: Smooth muscle does not contain tropomyosin complex but has instead Ca Calmodulin complex that carries out the phosphorylation.
Histology and Structure of Smooth Muscle Tissue
Smooth muscles have a length of 20-200µm and a thickness of 3-10µm. In the center of the smooth muscle is the nucleus which is cigar shaped during contraction. Smooth muscles cytoplasm is eosinophilic made of filaments.
Smooth muscle cell originates from mesoderm. Cell membrane has invaginations around itself. The cells remain intact due to the connective tissue beneath and the basal lamina. Muscle cells are spindle in shape. Smooth muscle has thick and thin filaments, but lack sarcomeres thus not forming a striated pattern. When observed under microscope its cytoplasm contains huge amount of actin and myosin.
Actin and Myosin
The muscle contraction proteins are actin and myosin. Actin filaments are spread everywhere and are connected to dense bodies. Myosin filaments are beneath actin filaments. When observed under electron microscope, it appears as black bodies. The smooth muscles are present in various organs such as
a) In stomach and intestine
b) In the lymphatic and blood vessel
c) In the ciliary muscle and eye
d) In the bladder
e) In skin
f) In male and female reproductive tract
g) In respiratory system
h) In urinary system
Types of Smooth Muscle
There are two types of smooth muscle and they are
a) Single Unit Smooth Muscle (Visceral): As the name suggest it functions together as a single unit.
b) Multiunit Smooth Muscle: Due to multiple type they cannot work together and function independently.
a) Single Unit Smooth Muscle (Visceral)
These cells forms the inner lining of various organs in the body. Example in the gastrointestinal tract digestion of food, reproductive system, urinary bladder, circulatory system and also in eyes where it can change its shape and size. These are also found in the blood vessel and are responsible for the contraction and relaxation of blood vessel. They have gap junctions thus, can work collectively.
b) Multiunit Smooth Muscle
These muscles are found in the hair follicles, lungs, pili muscles, eye muscles and they help in lens formation and control the amount of light that can pass. They do not have gap junctions; thus, they work independently.
Smooth Muscle Function
There are various functions of smooth muscle and are:
a) Contraction: When muscles contract, they allow the movement. For example, in the gut smooth muscle allows the food to pass down.
b) Self -working: The smooth muscle function on their own, i.e they are voluntary because they are under the control of autonomic nervous system. Due to the smooth we can breathe according to our will. In presence of CO2, they vasodilates and in presence of oxygen it vasoconstricts.
c) Maintains Homeostasis: The smooth muscles present on the skin hair follicles maintain the temperature automatically when it’s too cold by raising the hair follicles. This maintains body heat.
Smooth Muscle Dysfunction
It is a disorder or disease of smooth muscle which is deadly. It gets triggered due to disorder of smooth muscle throughout the body. It is supposed to be hereditary. The treatment of this disease is anti-smooth muscle antibodies like lupus or hepatitis. It is said to be deadlier because muscle failure will lead to a major problem. Many organs being connected to smooth muscle can halter the functioning of the body.
Smooth Muscle Action Potential
To start a contraction in the smooth muscle cell, membrane potential is required. Although the action potential of smooth muscle cell is slow but stands for a longer duration. For the smooth muscle, sodium channels are responsible, which open quite slowly in smooth muscle cell.
Smooth Muscle Citations
- Regulation of Airway Smooth Muscle Contraction in Health and Disease. Adv Exp Med Biol . 2019;1124:381-422.
- Pulmonary Smooth Muscle in Vertebrates: A Comparative Review of Structure and Function. Integr Comp Biol . 2019 Jul 1;59(1):10-28.
- Smooth muscle contraction and relaxation. Adv Physiol Educ . 2003 Dec;27(1-4):201-6.
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Law of Segregation: Definition, Principles, and Examples
Continue ReadingMendel's Law of Segregation
Gregor Mendel, the pioneer of genetics, published his results in 1860, which were originally controversial at the time but gradually gained momentum and became so generally recognised that they opened the way for the science of genetics to be founded. Based on his experiments with pea plant reproduction, he developed three separate rules of inheritance. His research clarified how genetic characteristics are passed down from generation to generation.
These rules have substantially increased our understanding of genetic inheritance and led to the development of novel experimental methodologies. The following are three different Mendel inheritance laws:
• The Law of Segregation
• The Law of Independent Assortment
• The Law of Dominance
Law of Segregation Definition
It’s also known as the first law of inheritance. The segregation law stipulates that:
“During the formation of gametes, the two copies of each genetic component separate to guarantee that each parent’s offspring inherits one element.”
“During the gamete’s development, each gene is segregated such that the gamete only has one allele for that gene.”
When a person creates gametes, the copies of a gene are separated such that each gamete only receives one copy. A gamete receives only one allele.
As the mechanism of meiosis was better understood, the exact proof of this was uncovered. The mother’s and father’s genes are divided during meiosis, resulting in two unique gametes with different character alleles.
Allele vs Gene
An allele is a distinct version of a gene; a gene is an important portion of the DNA that specifies a certain characteristic. Genes have a crucial influence on the manifestation of characteristics. Alleles are significant because they influence how a characteristic can be manifested.
Mendel claimed that the determining elements of heredity are distinct “unit factors” (now termed genes) that keep their integrity from the moment the zygote is created until it grows and produces its own gametes, despite his lack of understanding of chromosomes. The components of these paired “unit factors” segregate from one another and produce distinct gametes during gamete development.
What is Law of Segregation?
During meiosis, segregation occurs when allele pairs (different characteristics of the same gene) are separated so that they may be transferred to distinct gametes.
One of the Mendelian Laws of Inheritance, the Law of Segregation, states that the two members of a pair of alleles separate during gamete production. As a result, each gamete only has one member of each gene pair. The Law of Gamete Purity is a synonym. Compare and contrast the laws of Independent Assortment, Dominance, and Unit Characters.
Why is mendel's law of segregation known as the gamete purity law?
The Law of Segregation in genetics states that a gamete can carry either a recessive or dominant allele, but not both at the same time. This is why the law of purity of gametes is also known as the law of gametes purity.
Mendel’s first law was the segregation law. According to this theory, alleles separate during meiosis, according to this theory. The following are the essential principles of this law:
• For a gene, there might be more than one type of allele.
• When gametes are produced during the meiosis process, the allele pairs segregate, or separate.
• Two alleles are involved in the determination of a Mendelian trait: one is recessive and the other is dominant.
They stay together in pure form even when they are not affecting one other. They don’t mingle or merge in any way. Because of this, the segregation law is also known as the law of gamete purity. The segregation of two alleles of a gene generally happens during the production of gametes due to the segregation of homologous chromosomes during meiosis. Sister chromatids of homologous chromosomes separate during anaphase II, while tetrads (each tetrad consists of four chromatids of a homologous pair that arises through synapsis) separate during anaphase I.
A gamete is a kind of cell that participates in fertilisation. In humans, the female and male gametes are the egg and sperm, respectively. The X chromosome is the only kind of sex chromosome found in human eggs. The X or Y chromosome can be found in human sperm cells. The sex of the child is determined by this. A gamete will get one of the two alleles for any feature, including dominant or recessive traits, under the segregation law.
Law of Segregation Examples
A Mendelian trait’s alleles can be dominant or recessive, and they can be passed down from parent to kid (animal or plant). The colour characteristics of the flowers in plants, for example, are determined by the kind of allele inherited by the children. One of the alleles is passed down to the offspring of each parent plant. And the offspring’s allele sets will be determined by the chromosomes of the two gametes joining during fertilisation. During gamete development, these two sets of chromosomes are randomly separated (wherein meiosis is a part of the process).
Gregor Mendel was able to come up with the fundamental principles of inheritance in his paper outlining his work on the breeding and study of thousands of garden peas, subsequently described as Mendel’s Laws of Inheritance. The Law of Segregation, the Law of Independent Assortment, the Law of Dominance, and the Law of Unit Characters are the four laws in question.
Law of Segregation Principle and Example
The concept of segregation states that each individual has two alleles for each trait, and these alleles become segregated throughout the formation of gametes. In other words, each gamete has just one allele. The idea of segregation is important because it defines how genotypic ratios in haploid gametes are formed.
What does it imply when an allele is dominant?
The dominant allele is the one that has a physical manifestation (visible) on the human body as a result of its dominance. They have an effect even if the individual just has one copy of the allele. For example, between the yellow-flower trait and the white-flower trait, the dominant trait is the one that will emerge in a hybrid offspring, and the dominant allele is the one that codes for that feature.
In the absence of the dominant allele, the recessive allele will be expressed. Thus, children carrying the dominant allele will show the dominant characteristic, such as yellow flowers, while those carrying the recessive allele will show the recessive trait, such as white flowers.
In meiosis, where does the law of segregation apply?
In anaphase (I and II) of meiosis, Mendel’s Segregation Law is observed. The homologous chromosomes are separated into two daughter nuclei with different variants of each gene during the first meiotic division. The activity of homologous chromosomes during meiosis can help to separate alleles into different gametes for every genetic locus. The two distinct alleles for a single gene typically segregate when chromosomes divide into numerous gametes during meiosis, with each gamete acquiring one of the two alleles.
Why is the law of segregation so universally recognised?
The Law of Segregation is a widely acknowledged inheritance law since it is the only one that does not contain any exceptions, although the other two laws do. It claims that during fertilisation, each gene, which consists of two alleles that vary throughout the formation of gametes, one allele from both the mother and father, unites.
Law of Independent Assortment
It is also known as the second inheritance law, and it states:
“Separate allele pairs are handed right down to the next generation separately from one another, As a result, gene inheritance at one point within the genome has no pertaining to gene inheritance elsewhere”.
“Alleles of varied genes that are distributed during gamete production assort independently of one another, consistent with this rule.”
This law applies to qualities that are unrelated to one another, such as seed colour and form. When a person inherits two or more traits, they are assorted individually throughout the gamete formation process. As a result, the diverse characteristics have an equal chance of happening together. This means that one character’s inheritance will have no bearing on the inheritance of the other.
What is Law of Independent Assortment?
One pair of Mendelian traits differs from the other pair when two sets of Mendelian traits are merged into a hybrid. As a result, the alleles are self-contained and have no effect on the other alleles. For example, a round and yellow-shaped pea plant was cross-pollinated with a wrinkled green-shaped pea plant.
When does Law of Independent Assortment take place?
During metaphase I and anaphase I of meiosis, separate assortment laws may be seen while crossing over occurs in Prophase I. In metaphase, for example, the chromosomes line up in a random order along the metaphase plate.
Gamete cells are the end result of meiosis. Haploid cells, which have half the DNA of diploid cells, are known as gamete cells. It is a crucial element of reproduction that allows gamete cells to unite to create a diploid zygote, which has the DNA information needed for child development and the chromosomal number that is maintained over generations.
Principle of Independent Assortment
Independent assortment principles state that allele pairs are separated during gamete development, implying that characteristics are handed down to offspring independently of one another.
Law of Independent Assortment Importance
It’s crucial for various genetic variants in organisms. During the formation of gametes, for example, the gene or alleles coding for one trait segregate separately from the gene or alleles coding for another trait. It is also necessary for the generation of new genetic variants that increase population genetic diversity.
Law of Independent Assortment and Law of Segregation
• In the Mendelian inheritance pattern, both of them play a role.
• Both the first and second rules of Mendel shed light on the inheritance of alleles.
• Both laws are beneficial in expanding the diversity of individuals within communities.
Law of Independent Assortment and Law of Segregation
Mendel’s Segregation Law states that during gamete formation, two copies of each genetic component are different from one another. The law of segregation defines non-homologous chromosomal activity.
When two or more variables are inherited, the Independent Assortment law states that during the generation of gametes, an individual’s genetic factors assemble independently. This rule governs the action of alleles.
Mendel’s Law of Dominance
According to Mendel’s Law of Dominance:
“In a cross of parents who are pure for several characteristics, only one kind of trait will show up within subsequent generation. Offspring that are hybrid for a trait will show just the dominant trait, whereas children who are not hybrid would show recessive traits”.
“One component of a pair of characteristics dominates in inheritance while the other is repressed unless both variables in a pair are recessive. In the next generation of parents, there will only be one type of trait that is pure for contrasting features”.
What is Mendel’s Law of Dominance?
The silenced recessive allele will remain “dormant.” It will, however, be passed on to the following generation in the same manner as the dominant allele is. Only progenies with two copies of the repressed allele will express the suppressed characteristic.
When crossed by themselves, these children can also breed true. When Mendel crossed his pea plants numerous times, he discovered that when he crossed both pure tall and short plants, all young pea plants (F1) were tall. Yellow-seeded pea plants (F1) were made by crossing pure yellow-seeded and green-seeded pea plants.
Human Characteristics
There are about 200 characteristics that are passed down from generation to generation in humans. Hereditary characteristics are the names given to these intriguing aspects of human genetics. Dominant and recessive characteristics are among these genetic traits.
Dominant Characteristics
• The dominant trait is the one that emerges earliest or is most clearly displayed in a person.
• Dwarfism, high blood pressure, baldness (in men), abundant body hair, and six fingers are examples.
• Capital letters, such as AA or BB, denote a dominating characteristic.
Recessive Characteristics
• A recessive characteristic is one that is present at the genome level but is concealed and does not manifest in the organism.
• Normal development, normal blood pressure, not bald, minimal body hair, and normal five fingers are some examples.
• Small letters, such as aa or bb, are used to denote recessive traits.
A human’s physical, emotional, psychological, and health traits are all influenced by gene expression. Parents’ genes are handed on to their children.
Why can't these mendelian laws be applied universally?
Because certain characteristics do not follow Mendel’s inheritance pattern, the laws of independent assortment and dominance regulating inheritance are not always relevant. Non-Mendelian characteristics are those that are not Mendelian. Polygenic inheritance or numerous alleles, codominance, and incomplete dominance are examples of such characteristics.
Because certain alleles tend to be inherited jointly, the law of independent assortment is not always applicable. Sex-related characteristics are an example. They explain why some characteristics are shared by both men and women.
When chromosomes were discovered, Mendel’s hypothesis was confirmed, and meiosis was thoroughly defined in the years that followed. If the genes were on chromosomes, the two members of the pair would split during Anaphase I of meiosis as the homologous chromosomes migrate apart from each other toward the opposing ends of the dividing cell.
Importance of Mendel's Laws in Biology
Mendel’s rules are useful in plant and animal breeding because they allow for the production of desired varieties of plants and animals through hybridization. The required traits conveyed in various combinations can be linked and preserved in a single unique variety.
Because of Mendel’s segregation law and independent assortment law, cross hybridization has resulted in the development of numerous new disease-resistant and high-yielding agricultural products and ornamental plants.
Law of Segregation Citations
- Statistics of Mendelian segregation-A mixture model. J Anim Breed Genet . 2019 Sep;136(5):341-350.
- On the origins of the Mendelian laws. J Hered . Jan-Feb 1984;75(1):67-9.
- Limits of imagination: the 150th Anniversary of Mendel’s Laws, and why Mendel failed to see the importance of his discovery for Darwin’s theory of evolution. Genome . 2015 Sep;58(9):415-21.
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