Heredity and Evolution Science - Heredity and Evolution

Scientists believe that all life originated in:

In the F generation of a cross, progeny having different traits are produced in the ratio 3 : 1. State whether it is a monohybrid cross or a dihybrid cross? Give one example of such a cross.

State one characteristic which shows that the birds are very closely related to dinosaurs.

What are the four blood groups in humans?

Name two organisms which are now extinct and studied from their fossils.

How does the creation of variation in a species ensure its survival?

What is meant by a species? Give two examples of plant species and two of animals.

Name two animals having homologous organs and two having analogous organs. Name these organs.

In what way are homologous organs evidence for evolution?

Define ‘natural selection’.

Why are the traits acquired during the lifetime of an individual not inherited?

With the help of an example, explain how variation leads to evolution.

What evidence do we have for the origin of life from inanimate matter (lifeless matter)?

State Mendel’s second law of inheritance.

State the various factors which could lead to the formation of new species.

What is meant by dominant genes and recessive genes? Give one example of each.

There are five animals A, B, C, D and E. The animal A uses its modified forelimbs for flying. The animal B uses its forelimbs for running whereas the animal C uses its forelimbs for grasping. The animal D can live on land as well as in water and uses its forelimbs to prop up the front end of its body when at rest. The animal E which respires by using spiracles and tracheae uses wings for flying but its wings are analogous to the modified forelimbs of animal A.

1. What could the animals A, B, C, D and E be?
2. Why are the forelimbs of animals A, B, C, D called homologous organs?
3. What does the existence of homologous organs in animals A, B, C and D tell us about their ancestors?
4. Why are the modified forelimbs of animal A and the wings of animal E called analogous organs?
5. State whether animals A and E have a common ancestor or not.

X, Y, and Z are three animals. The animal X can fly but animal Y can only run on ground or walls. The forelimbs of animals X and Y have the same basic design but they are used for different purposes such as flying and running respectively. The animal Z became extinct an long time ago. The study of fossils of Z tells us that it had some features like those of X and some like those of Y. In fact, Z is said to form a connecting link in the evolutionary chain of X and Y.

1. What could the animals X, Y and Z be?
2. What name is given to the forelimbs like those of X and Y which have the same basic design but different functions?
3. Name one feature in which Z resembled X.
4. Name one feature in which Z resembled Y.
5. Which is the correct evolutionary chain involving X, Y and Z : X → Z → Y or Y → Z → X?

Explain how, sex is determined in human babies.

“Only variations that confer an advantage to an individual organism will survive in a population”. Do you agree with this statement? Give reason for your answer.

Fill in the following blanks with suitable words:
Genes always work in _________.

Fill in the following blanks with suitable words:
Most people have________ earlobes but some have________ earlobes.

Fill in the following blanks with suitable words:
The_______ chromosomes for a______ are XX whereas that for a______are XY.

Fill in the following blanks with suitable words:
The human forelimb and bat’s forelimb are an example of ________ organs whereas an insect’s wing and a bat’s wing are an example of _______ organs.

Fill in the following blanks with suitable words: The scientific name of all human beings is ________ .