(a) [•] Homologous organs:- Organs with common origin and structure but different function.

Examples:- Forelimbs of Amphibians, Reptiles, Birds and Mammals.

[•] Analogous organs:- Organs which perform similar function but have different origin and structure.

Examples:- Wings of Bat, Birds, and Insects.




(b) There are actually four main processes that are the cause of Evolution. They are:-
[•] Mutation.
[•] Geographical isolation.
[•] Genetic drift.
[•] Natural selection.

* Mutation occurs when something causes the genes of an organism's DNA to change, this can be for various reasons.

* Geographical isolation occurs when two population of the same species gets separated by the physical barrier (environmental conditions) like wind, water and niche (place).

* Genetic drift occurs when the gene present in the organisms changes randomly due to by chance only, irrespective of its advantageous or not in their (Organisms) population.

* Natural selection occurs when the organisms are to get survival from the enemies by changing in the frequency of triats, which results in the adaptation of the organisms population in the environment better and leads to give survival advantage.



Note:-These above four main processes of Evolution is to give the variation in organisms and makes them to survival of the species by changing their traits in the organisms.

Homologous and Analogous Organs:

Homologous organs are those that have a similar basic structure and developmental origin, but may have different functions in different organisms. They are evidence of a common ancestry. For example, the forelimbs of vertebrates such as humans, cats, whales, and bats have the same basic structure, with the same set of bones arranged in similar ways. However, they have different functions - humans use their forelimbs for grasping, cats for climbing, whales for swimming, and bats for flying. These organs are considered homologous because they share a common structure, despite their different functions.

Analogous organs, on the other hand, are those that have a similar function but a different structure and developmental origin. They do not provide evidence of common ancestry. For example, the wings of birds and insects have similar functions - both are used for flying. However, their structures and developmental origins are different. Birds have feathers and wings made of bones, while insects have wings made of chitin. These organs are considered analogous because they have a similar function, but their structures and origins are different.

Process of Evolution:

Evolution is the process by which species gradually change and diversify over time. It is driven by several mechanisms, including natural selection, mutation, genetic drift, and gene flow. The process of evolution can be broadly explained in the following steps:

1. Variation: Within a population, there is variation in traits due to genetic differences caused by mutations and genetic recombination during reproduction.

2. Overproduction: Organisms tend to produce more offspring than can survive, leading to competition for resources.

3. Natural Selection: Individuals with traits that are advantageous for survival and reproduction are more likely to survive and pass on their genes to the next generation. This process is known as natural selection.

4. Adaptation: Over time, the frequency of advantageous traits increases in the population, leading to the evolution of adaptations that enhance survival and reproductive success.

5. Speciation: If populations become isolated from each other and undergo different selective pressures, they may accumulate enough differences to become separate species.

6. Extinction: Species that are unable to adapt to changing environments or face competition from other species may become extinct.

7. Gradual Change: Evolution is a gradual process that occurs over long periods of time. Small changes accumulate over generations, leading to significant differences between species.

By studying homologous and analogous organs, scientists can gain insights into the evolutionary relationships between different species and the processes that have shaped life on Earth.