JSIERT

Those organs with the same basic structure and similar embryonic origin but different functions are called homologous organs. These organs follow the same basic plant of the organisation during development, but in adults got modified to perform different functions as an adaptation to different environments. Those organs which have a different basic structure and embryonic …

Distinguish between homologous organs and analogous organs. In which category would you place the wings of a bird and a bat? Justify your answer by giving a suitable reason. (Delhi 2012) Read More »

(a) Planaria, insects, octopuses and vertebrates cannot be grouped based on an eye. Eyes of insects, octopuses, Planaria and vertebrates are analogous organs which have developed over a generation as an adaptation for a similar function. They represent convergent evolution where distantly related groups develop similar functional structures as an adaptation for the same function. …

(a) Planaria, insects, octopuses and vertebrates all have eyes. Can we group the eyes of these animals to establish a common evolutionary origin? Justify your answer.
(b) “Birds have evolved from reptiles”. State evidence to prove the statement. (Delhi 2015) Read More »

Introduction : Mendel (1856-1863) conducted hybridization experiments on garden peas( Pisum sativum). During that period, he chose some characteristics of the peas and conducted some cross-pollination on the pea lines that showed stable trait inheritance and underwent continuous self-pollination. The two experiments lead to the formulation of Mendel’s laws known as laws of inheritance which are: …

Write Mendel’s laws. Read More »

Introduction Mendel (1856-1863) conducted hybridization experiments on garden peas( Pisum sativum). During that period, he chose some characteristics of the peas and conducted some cross-pollination on the pea lines that showed stable trait inheritance and underwent continuous self-pollination. Why was Pea Plant Selected for Mendel’s Experiments? He selected a pea plant for his experiments for …

Write Mendel’s Laws of Inheritance. Why was Pea Plant Selected for Mendel’s Experiments? What are the Mendels plant’s traits Read More »

(a)  Homologous organs perform different functions in different species, they share a common basic structure and embryonic origin. For example, the forelimbs of a frog, lizard, bird and human being show similarities in basic structure.  Despite the fact that these organs serve very different functions, the basic similarity in the forelimbs of these various vertebrates …

Explain with the help of an example each, how the following provide evidences in favour of evolution:
(a) Homologous organs
(b) Analogous organs
(c) Fossils (Delhi 2017, AI 2015, Delhi 2011) Read More »

Evolution is a sequence of gradual changes from simple to complex life forms. Many organs adapt to new functions as a result of evolution. Homologous organs are those that have a similar basic structure and embryonic origin but carry out different functions in various species. Divergent evolution leads to homologous structures. Homology suggests a common ancestry. Example, …

During the course of evolution, organs or features may be adapted for new functions”. Explain this fact by choosing an appropriate example. (2020) Read More »

(a) (i) Broccoli and cabbage – Homologous organs(ii) Ginger and radish – Analogous organs(iii) Forelimbs of birds and lizards – Homologous organs(iv) Wings of a bat and wings of a bird – Analogous organs (b) Homologous organs have the same fundamental structure but different in function Analogous organs have different internal structures but similar functions.

Speciation is the process through which new species arise from already existing ones. In the process of speciation, both genetic drift and natural selection are crucial. Natural selection is the process through which nature chooses features that are advantageous to the species in a particular environment. For example, beetles change their colour when they reproduce. …

What is speciation? Explain in brief the role of natural selection and genetic drift in this process. (Foreign 2016) Read More »

There are three ways the population of people with a specific trait may grow:(i) Genetic drift: This is the random change in gene frequency that results from random fluctuations In this scenario, a particular characteristic with limited adaptive value and a survival advantage may become more common. (ii)Natural selection is the process through which nature …

Describe any three ways in which individuals with a particular trait may increase in population. (AI 2011) Read More »

If we breed many mice, every mouse that is born will have a tail like its parents. Now, if we surgically remove the tails and then breed the mice once more, we continue to produce mice with tails. This is due to the fact that removing a mouse’s tail does not alter the genes in …

“An individual cannot pass on to its progeny the experiences of its lifetime”. Justify the statement with the help of an example and also give a reason for the same. (Foreign 2012) Read More »