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प्रश्न
What do you mean by ‘Connecting Links’? Give one example.
उत्तर
1. Organisms referred to as ‘connecting links’ are those which are structurally intermediate between two different groups.
2. Connecting links can be found among organisms that are still living.
3. Eg. :(a) ‘Peripatus’ has segmental nephridia, thin cuticle, and parapodia - like appendages as in Annelida. At the same time, it has a trachea and open circulation as in Arthropoda.
(b) The duck-billed platypus lays eggs like reptiles and has hair and mammary glands like mammals.
(c) Lungfish, though a fish, breathes air through its lungs.
4. These organisms point strongly to the fact that mammals have evolved from reptiles and amphibia from fishes.
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संबंधित प्रश्न
Egg laid after fertilisation is made up of a single cell.
Find the odd one out:
Amoeba, Euglena, Planaria, Paramoecium
What is the name of the reproductive process :
which involves two parents?
Which type of reproduction :
does not involve gametes?
Name two animals which reproduce asexually.
Which of the following organisms reproduce by sexual method and which by asexual method?
Amoeba, Cats, Humans, Hydra, Birds
What are the two general methods of reproduction in organisms?
What is the importance of DNA copying in reproduction? Explain with an example.
Name two animals which undergo external fertilisation.
Fill in the following blank with suitable word :
The union of a sperm nucleus with an egg nucleus is known as.......... and results in a .........egg.
State whether the following statement is true (T) or false (F):
Dogs and cats reproduce from two parents.
Why is reproduction necessary for living organisms?
Give reason for the following:
Vegetative propagation is practised for growing only some type of plants.
Match the following:
| Column ‘I’ | Column ‘II’ |
|
(1) Inhibits plant growth
|
(a) Breaks large fat globules into smaller ones
|
|
(2) Cytokinins
|
(b) Auxins
|
|
(3) Cellular respiration
|
(c) Mitochondria
|
|
(4) Bile
|
(d) Promote cell division
|
|
(e) Abscisic acid
|
Explain the term: Pollination.
By which process do green plants synthesize their food?
Answer the following question.
The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on. Some degree of sexual maturation does not necessarily mean that the mind or body is ready for sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of the population.
(a) List two common signs of sexual maturation in boys and girls.
(b) What is the result of reckless female foeticide?
(c) Which contraceptive method changes the hormonal balance of the body?
(d) Write two factors that determine the size of a population.
Multiple choice question.
In ovule, meiosis occurs in ______
If diploid chromosome number in a flowering plant is 12, then which one of the following will have 6 chromosomes?
The number of nuclei present in a zygote is _______.
Multiple choice question.
Presence of beard in boys is a _______.
Self-incompatibility is found in flowers of plants _______.
The example of dicot endospermic seed is ______.
Which is the most common type of endosperm in angiospermic families?
Nebenkern is ______.
Nervous system develops from ______ of embryonic layer.
The average period of pregnancy in human lasts for ______ days of pregnancy.
What are the causes for the extinction of animals?
Reproductive part of a plant is ______.
The plant which propagates with the help of its leaves is ______.
Explain the term reproduction.
Assertion and Reason types of Question.
Assertion: In potatoes, shoot arises from eyes.
Reason: Eyes represent the buds.
In the list of animals given below, hen is the odd one out.
| human being | cow | dog | hen |
The reason for this is
Observe the following figures.
 |
 |
 |
|
| (a) | (b) | (c) | (d) |
- Identify the stages (a) to (d) in figure during development of human baby.
- Arrange the stages in correct sequence of development.
- Explain the development that takes place in any one stage.
Choose the correct meaning of reproduction.
