Short Questions and Answers
One Mark Questions with Answers
1. Early atmosphere possessed
(b) Water and hydrogen
(d) All the above
Answer: (d) All the above
2. Coacervates were
(a) colloidal complexes
(d) both b and c
Answer: (a) colloidal complexes
3. The earliest living beings were
(d) spontaneously generated
Answer: (b) chemoheterotrophs
4. Wings of insects and birds show an evolution
Answer: (b) convergent
5. A connecting link is
(d) All the above
Answer: (b) Peripatus
6. Which one is vestigial in humans?
(a) auricular muscles
(b) scalp muscles
(c) abdominal muscles
(d) All the above
Answer: (d) All the above
7. Mesozoic is
(a) age of fishes
(b) age of amphibians
(c) age of reptiles
(d) age of trilobites
Answer: (c) age of reptiles
8. Flippers of Seal are
(b) fore limbs
(c) hind limbs
Answer: (b) fore limbs
9. The first vertebrates and first land plants appeared during
Answer: (a) Ordovician
10. Appearance of an ancestral trait is
(d) both a and b
Answer: (c) atavism
11. Recapitulation theory was proposed by
(a) Van Baer
Answer: (c) Haeckel
12. Sum total of genes in a population is called
(c) gene pool
Answer: (c) gene pool
Two Marks Questions with Answers
1. Describe one example of adaptive radiation.
Answer: Adaptive radiation is the formation of different species from a common ancestor with new species adapting to different ecological niches. Darwin’s finches present in Galapagos Island have evolved from mainland finches. On the islands they underwent adaptive radiation in shape and size of, food habits, colour of feathers, body size etc. to form distinct species.
2. Differentiate between Darwinism and Neo- Darwinism.
Answer: Darwinism is the theory proposed by Darwin. Neo-Darwinism is modification of Darwin’s theory in order to remove its defects and incorporate latest information. Darwinism does not give reason for the appearance of variations. Neo Darwinism explains the origin of various types of variations. Darwinism believes that all useful variations are inheritable whereas Neo darwinism believes that only genetic variations are inheritable.
3. Differentiate between lamarckism and Darwinism?
Answer: Lamarckism believes in the presence of an internal vital force in all organisms while Darwinism does not believe in the existence of any internal vital force. Lamarckism considers perfecting principal to be guiding people for all the organisms to achieve harmony with environment while according to Darwinism nature selects only those individuals which are adapted to the environment in which they live.
4. What is atavism? Give examples.
Answer: It is the reappearance of a remote ancestral form of a trait which has otherwise become reduced and nonfunctional in the present generations. Atavism confirms the retrogressive evolution. (a) Human tail- Some babies develop a small tail which is otherwise absent in human beings. The same is removed. (b) Movement of pinnae in human beings- Some persons are able to move pinnae somewhat irregularly. It is caused by atavistic development of auricular muscles. (c) Dense body hairs- Some male have dense growth of body hair.
5. Describe one evidence of evolution from embryology.
Answer: Embryology is the development of embryo from zygote till it becomes an offspring. Embryology provides a number of evidences in support of evolution. Similar early development of embryos- All animal embryos begin their development from a single celled zygote, forming first a solid ball of cells called morula, a hollow ball or blastula and two layered gastrula. The two layers of gastrula from all the structures in diploblastic animals like coelenterates. In others it adds a third layer. Three germ layers occur from platyhelminthes to chordates. They are called triploblastic animals. The germ layers produce similar types of structures in all the animals.
Three Marks Questions with Answers
1. What are homologous organs?
Answer: They are organs which possess a similar internal structure and similar development but often have different form and function. The phenomenon of producing functionally different forms from structurally similar structure is called divergent evolution. Examples: (a) Vertebrate fore-limbs- Forelimbs of various tetrapods, weather a frog, lizard, bird whale, horse or man have a similar internal structure, similar embryological development and similar types of muscles, nerves and blood vessels. The limbs are however quite different in external form and function. They are used for leaping in frog, creeping in lizard, flying in bird and bat, swimming in whale, running in horse, galloping and tearing in cheetah and grasping in man. (b) Insect legs are used for clinging in lice, digging in mole cricket, swimming in water beetle, squatting in mosquito, jumping in grasshopper, collection of pollen grain in honey bee and grasping in praying mantis
2. What are analogous organs?
Answer: Organs having similar outward form and function but quite different in anatomy and development. The phenomenon indicates evolution of similar functional structures from unrelated organs. It is called convergent evolution or homoplasty. Examples: (a) Wings of insects birds and bats perform the same function. Insect wings are integumentary outgrowths having hollow tubes. Blood, muscles and nerves do not occur inside the wings but a restricted to base. Wings of birds are modified fore limbs which possess flesh, skin, muscles, blood, nerves and covering of feathers. In bats the wings are modified fore limbs but possess skin extensions between elongated fingers instead of feathers.
Fins and flippers-Fins present in fishes are used for balancing and swimming. Flippers are present in whale and dolphin. They are used in swimming. Flippers are pentadactyl fore limbs while fins are cutaneous structures. The two are analogous.
3. What are the salient features of mutation theory of evolution?
Answer: Mutations constitute the raw material of evolution evolution cannot occur without the appearance of Nutrition mutations appear all of a sudden the same mutations can appear in more than one individual at the same time as well as at different times mutations do not fluctuate around the normal traits of the species they are not connected to the normal by any intermediate forms expression mutations at in full constancy at once that is they Express their effect immediately imitations develop in every conceivable degree and direction mutations are genetic variations which are inheritable on the basis of their effect mutations are progressive retro dresses with aggressive for in constant beneficial mutations are selected by nature extremely harmful or Lethal mutation Sarim eliminated useless and some harmful mutations were produced in the progeny new elementary species originates early due to large materials they are also formed by the accumulation of small mutations evolution is not a gradual process but is instead jerky or discontinuous process mutability is fundamentally different from the fluctuating variability proposed by Darwin.
4. Describe evidences provided by taxonomy that support evolution.
Answer: Resemblance amongst organism: Classification is based on formation of groups and subgroups. The grouping is carried out on the basis of resemblances and morphological, anatomical, bio-chemical, cytological and other traits. All vertebrates process common characters of
(a) presence of endoskeleton of cartilage, bone or both. (b) Presence of notochord which gives rise to the vertebral column. (c) Heart is ventral. (d) Occurrence of pharyngeal gill slits atleast in embryo stage. (e) Hollow dorsal nervous system.
Similarly all bryophytes are characterized by (i) absence of roots and presence of rhizoids for fixation.(ii) Absence of vascular tissues.(iii) Plant body represented by the gametophyte.(iv) Parasitic saprophytes. Resemblances are despite the fact that vertebrates vary from fishes, amphibians, reptiles, birds and mammals. Similarly, bryophytes vary from thalloid liverworts, hornworts, jungermanniales to mossess of several types. Presence of similar characters in a group or subgroups clearly suggests a common ancestry.