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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
Name the scientist who put forward the most popular model of DNA.
Draw a diagram of DNA showing genes.
Define reproduction.
How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
Why is DNA copying an essential part of the process of reproduction?
Egg laid after fertilisation is made up of a single cell.
What is the name of the reproductive process :
which involves only one parent?
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
Match the organisms given in column I with the methods of reproduction/propagation given in column II :
| Column I | Column II | |
| (i) Plasmodium | (a) Spore formation | |
| (ii) Spirogyra | (b) Leaves | |
| (iii) Jasmine | (c) Regeneration | |
| (iv) Apple tree | (d) Budding | |
| (v) Bryophyllum | (e) Binary fission | |
| (vi) Potatoes | (f) Layering | |
| (vii) Rhizopus | (g) Fragmentation | |
| (viii) Hydra | (h) Tubers | |
| (ix) Planaria | (i) Cuttings | |
| (x) Leishmania | (j) Multiple fission | |
| (xi) Sugar cane | (k) Grafting | |
| (xii) Rose |
What are the two general methods of reproduction in organisms?
Why is variation during reproduction beneficial to the species but not necessarily for the individual?
Asexual reproduction is :
(a) a fusion of specialised cells
(b) a method by which all types of organisms reproduce
(c) a method producing genetically identical offspring
(d) a method in which more than one parent are involved
The protozoan having a flagellum at its one end is :
(a) Amoeba
(b) Paramecium
(c) Hydra
(d) Leishmania
In asexual reproduction, two offsprings having the same genetic material and the same body features are called :
(a) callus
(b) twins
(c) clones
(d) chromosomes
State whether the following statement is true (T) or false (F):
Producing life is called respiration.
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?
List any two different forms asexual reproduction.
Write the full form of DNA.
Explain the term Reproduction.
By which process do green plants synthesize their food?
Multiple choice question.
The ploidy level is not the same in ______.
If diploid chromosome number in a flowering plant is 12, then which one of the following will have 6 chromosomes?
Multiple choice question.
Point out the odd one.
The example of dicot endospermic seed is ______.
Draw a well labelled diagram of T.S. anther.
Nervous system develops from ______ of embryonic layer.
The average period of pregnancy in human lasts for ______ days of pregnancy.
Match the following.
| Column I | Column II |
| Fission | Spirogyra |
| Budding | Amoeba |
| Fragmentation | Yeast |
What will happen if you cut planaria into small fragments?
Identify the chromosome number of the endosperm in the following case. In an angiosperm a female plant having 2n = 24 is crossed with a male plant having 2n = 12.
Assertion and Reason types of Question.
Assertion: In Banyan prop roots grow horizontally from the tree.
Reason: They give additional support to the tree.
Which of the following nucleus is unlike other nuclei in the female gametophyte of angiosperms?
Give reason for the following:
All multicellular organisms cannot give rise to new individuals through fragmentation or regeneration.
Choose the correct meaning of reproduction.
