Plant Ecology II Guess Paper 2024 MSc Botany 3rd Semester .More than a century ago, in 1958, Charles Darwin (1809-1882) and Alfred Russel Wallace (1823-1913) combinedly credited the theory of evolution by natural selection and published the book “Origin of species”.Plant Ecology II Guess Paper 2024 MSc Botany 3rd Semester.In 1859, Darwin separately published the book called “On the origin of species by means of natural selection”.
Plant Ecology II Guess Paper MSc Botany 3rd Semester
After the death of Darwin, Neo-Darwinism theory was develope base on genetic character whe the gene was discovere in 1901 by American scientists Margon, Shutton, etc.Plant Ecology II Guess Paper MSc Botany 3rd Semester.
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Plant Ecology II Guess Paper MSc Botany 3th Semester
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Facts that influenced Darwin’s thought or Development of the theory of natural selection
- In 1831, Darwin was the naturalist on the Voyage when he was just 22 years old. As a naturalist, he observed, collected, and analyzed specimens of plants, animals, rocks, and fossils. He spent more than three years exploring nature on the island and distant continents.
- Darwin made many observations during the long Voyage, which helped him develop the theory of evolution.Plant Ecology II Guess Paper MSc Botany 3rd Semester
- Darwin follows the idea of Lamarck and assumes that species can change over time. Fossils he found helped conveniently follow Lamarck’s theory.
- From Charles Lyell’s book “Principles of Geology”, Darwin concluded that there had been enough time for evolution to cause the great diversity of life because he saw the earth and its life were very old.
Darwinian theory of natural selection
- Darwin-Wallace theory states that “The change in species by the survival of an organismal type exhibiting a natural variation that gives it an adaptive advantage in an environment, thus, leading to a new environmental equilibrium, is evolution by natural selection”.
- The natural selection process is a continuous process of trial and error on an enormous scale for all living matter.
- Natural selection includes the following five elements (factors or causes of natural selection).
- The universal occurrence of variation:
- Every group of organisms (animal and plant) may differ in many ways, known as variation. The Darwin and Wallace period did not know the source of variation and assumed it might be one of the innate properties of the organism. Still, now we know that inherite variations are caused by mutation.
- An excessive natural rate of multiplication:
- Without environmental checks, every species has great reproductive potential (reproductive rate tends to increase geometrically). If all the species remained alive and reproduced, it would soon be challenging to survive, obtain food, and crowd all other species from earth.
Struggle for existence:
- There is an interspecific or intraspecific, or environmental struggle for survival (competition for food, mates, space, and as well as survival in drought or cold).
- The consequent elimination of the unfit and the survival of only those that are satisfactory adaption:
- Some of the variations shown by living things make it better adaption for them to survive; others are handicaps that bring about the elimination of the possessors. The core of the natural selection theory is the idea of the survival of the fittest.
Criticisms of Darwinism or natural selection theory
- Darwin did not mention vestigial organs, which are in animals.
- The role of mutation in the origin of new species is not include. Without mutation, new species never evolved by natural selection.
- Variation, whether genetic or somatic, because only genetic variations are heredity.
- Darwin’s theory became a failure in Human being due to these reasons; the human population never becomes constant, not only struggling for existence other also continuing life cycles like beggars, and instead of survival, the fitness in man only arrival become most fitted.
Types of natural selection
Population geneticists have categorized three types of natural selection that can occur in nature. These are as follows:
3. Disruptive selection
- In this selection, two adaptive traits are selected when the population exists in a heterogeneous environment. It favors the extreme if they have better traits or fitness and intermediates are disadvantageous. This selection results in diversification concerning traits.
- For example, an area that has black, grey, and white bunnies contains both white and black rocks. Natural selection will favor both the traits of white and black since they both prove useful for camouflage. The intermediate trait of grey does not prove useful so selective pressure act against the trait.
The evolutionary biologist also recognized sexual selection and group and kin selection.
- Sexual selection
- Most species of animals are dimorphic (male and female). Males and females are different in terms of color, specialized song patterns, behaviors, sex organs, capability, etc.
- Sexual selection is directly related to differential reproduction, including finding and acquiring a mate, copulation, fertilization, and parental care.
- Those organisms whose more capable of securing mates and is more fitted to the environment. Sexual selection aims to reproduce in which an individual needs to be able to find and protect a mate and produce viable offspring.
- In 1938, Huxley recognized two types of sexual selection; Epigamic selection (based on the choice made between male and female) and Intrasexual selection (this selection is based on the interaction between animals of the same sex, generally between males).
- Group and kin selection
- Group selection is a selection of a group of individuals, favoring one group over the other, leading to the evolution of a trait that is group advantageous.
- The altruistic behavior of an individual involved in kin selection occurs when natural selection favors a trait that benefits related group members.
Protected areas designed for the conservation of plants and animals recognized by UNESCO are known as biosphere reserves. They protect the local wildlife and its diversity. Terrestrial, marine and coastal ecosystems are all included in biosphere reserves. These reserves advocates strategies that balance biodiversity solution and sustainable human usage. It promotes sustainable development appropriate for integrating people and nature and where solutions are sought for biodiversity conservation, economic growth, research, and education. In Yangambi, the Democratic Republic of the Congo, the first biosphere was discovered. Other biosphere reserves are Fuerteventura Reserve in Spain, Gran Arenal Biosphere Reserve in Australia, and Bliesgau Biosphere Reserve in Germany.
Importance of Biosphere
- The components of the biosphere are categorized as biotic, abiotic, and energy components. Abiotic components include non-living elements such as the lithosphere, atmosphere, and hydrosphere, while biotic components include plants, animals, and microorganisms.
- The plants of the biotic communities supply us with raw materials such as food, fuel, and fibers to survive.
- The decomposers of the biosphere play a lead role in the decomposition and biological modification of toxins and other harmful components.
- Naturally available compounds in the terrestrial biosphere help to provide pharmaceutical compounds in the pharmaceutical industries.
- The biosphere’s composition can be studied and managed to serve as an effective marker for regulating the amount of terrestrial pollution.