CHAPTER 5:- ORIGIN AND EVOLUTION OF LIFE

Q.:  Write a short note on Anthropoids.

Ans. The sub order Anthrapoidea includes three types of groups:

A) New world monkeys: 1) these are found in south and Central America.

2) Flat nose, with widely separated nostrils.

3) Long prehensile tail.

4) Primitive dentition with 36 teeth.

5) e.g. squirrel monkey, spider monkey etc.

B) Old world monkeys: 1) they are found in tropical regions of Africa and Asia.

2) Narrow nose.

3) Short non-prehensile tail.

4) Dentition with 32 teeth.

5) e.g. baboons, macaques, langurs etc.

C) Hominoid: 1) it includes apes and man.

2) It possible that they might have evolved from common ancestor simultaneously.

3) e.g. Gibbons, Chimpanzee, orangutans, gorilla, etc.

Q.: Write a notion distinguishing characters of apes.

Ans.: 1) Face is prognathous, forehead slanting,

2) Snout is protruded with flat nose.

3) Large teeth, diastema or simian gap is presenting upper jaw between incisor and canines to accomodate canine of lower jaw.

4) Chin is absent.

5) Brow ridges are heavy and protruded.

6) Foramen magnum in skull is directed backward and lumbar curve is absent.

7) Pelvic girdle narrow.

8) Tail is absent.

9) Forelimbs are longer than Hind Limbs.

10) Semi erect with Quadrupedal locomotion.

11) Cranial capacity is 400 to 600 c.c.

Q.: Write a note on general characters of modern man.

Ans.: 1) Orthognathous face development of high forehead.

2) Skull dome shaped, elevated nose.

3) Dental arch rounded parabola and jaws are small.

4) Development of prominent chin.

5) Foramen magnum is directed downward. and lumbar curve is well developed.

6) Pelvic girdle is broad basin like.

7) Complete erect posture with bipedal locomotion.

8) Forelimbs are shorter than Hind limbs.

9) Cranial capacity about 1450 c.c.

10) Development of articulated speech.

Q.:  Explain the phylogenetic relationship between ape and man.

Ans.: The phylogenetic relationship between ape and man can be explained with the help of following features.

1) Absence of tail.

2) Comparatively larger head.

3) Broad chest due to flattening of sternum.

4) Molar teeth with five cusps.

5) Capable of sound production.

6) Menstrual cycle in females.

7) Highly developed facial musculature for expressions.

8) Remarkable similarities in DNA, Haemoglobin and albumin molecules of chimpanzee, gorilla and man.

Q.What are the palaeontological evidences related to dentition in human evolution?

Ans.:1. The present day men evolved from an ape like ancestor.

2. The fossils show gradual change in dentition i.e. arrangement of teeth in jaws.

3. Large pointed canines were reduced to small size.

4. Incisors became straight.

5. Rounded parabola type jaws were developed.

6. Number of premolars was reduced from 3 to 2.

7. Grinding teeth gradually changed to omnivores nature of diet.

Q. 85. What are the various evidence in terms of fossils related to skull in human evolution?

Ans.:1. Skull and cranial capacity showed remarkable changes during human evolution.

2. The early human ancestors shown small-elongated slightly flattened skull  with low cranial capacity.

3. Skull bones became compact with firm arrangement, which resulted in the development of changes in face and cranial capacity.

4. It can be demonstrated by the following facts:

(a) Small elongated skull changed into a large skull.

(b) Cranial capacity was increased from 650cc to 1400cc.

(c) Thick eyebrow ridges changed to normal size.

(d) Slanting for head changed to vertical normal forehead.

(e) Receding chin changed into prominent chin.

(f) Flat nose changed into narrow elevated nose.

Q. Compare the skull of ape with man.

Ans.:1. Primates evolved towards man showing variuos changes in skull vertebral  columns, limbs etc.

2. Apes have small cranial capacity about 450cc while that of man is 1400cc.

3. In apes forehead is slanting and brow ridges are prominent while men show vertical forehead and reduced brow ridges.

    4. Absence of chin is observed in apes while man is characterized by presence  of well-developed chin.

5. In apes dentition pattern is U-shaped with small incisors and large canines while in humans teeth are arranged in rounded [parabola type with canines and incisors are small and of equal length].

Q. Bipedal nature and opposable thumb are the gifts of evolution to man.

Ans.:1. During the course of evolution man developed erect posture.

2. Development of erect posture brought changes in pelvic girdle and foot.

        3. It resulted into bipedal locomotion with heel and toes.

4. It permitted fast locomotion and helps in migration.

5. Hands became free which are used for different skillful works.

6. Opposable thum is reponsible for giving firm grip.

7. It resulted into balancing of the head and body weight on two legs.

Q. What are the evolutionary changes took place during human evolution?

Ans.:1. The process of development started in Oligocene epoch nearly 35 million 

years ago and completed during Pleistocere epoch about 10 thousand year 

ago.

2. The cause of development show various changes in characters.

(a) small elevated skull changed to large rounded skull.

(b) Cranial capacity increased from 450 CC to 1600 CC [in cro magnon                         man] and then decreased to 1400 in modern man.

(c) Prognathus sloping face changed to flat vertical.

(d) Distinct chin was developed.

(e) Teeth became small and jaw changed into rounded parabola type.

        (f) Foramen magnum moved downward and four distinct curvatures                             were developed in vertebral column.

(g) Quadruped locomotion changed to biped and hands became free.

(h) Skillful use of brain and hands were used for different works.

FOR CHARACTERS OF DIFFERENT ANCESTRAL STAGES REFER ONY TEXTBOOK. NO NEED TO STUDY ADDITIONAL CHARCTERS FOR STATE BOARD EXAM.