Notes Human Evolution ICSE Class 10 Biology

Students should refer to Human Evolution ICSE Class 10 Biology notes provided below designed based on the latest syllabus and examination pattern issued by ICSE. These revision notes are really useful and will help you to learn all the important and difficult topics. These notes will also be very useful if you use them to revise just before your Biology Exams. Refer to more ICSE Class 10 Biology Notes for better preparation.

ICSE Class 10 Biology Human Evolution Revision Notes

Students can refer to the quick revision notes prepared for Chapter Human Evolution in Class 10 ICSE. These notes will be really helpful for the students giving the Biology exam in ICSE Class 10. Our teachers have prepared these concept notes based on the latest ICSE syllabus and ICSE books issued for the current academic year. Please refer to Chapter wise notes for ICSE Class 10 Biology provided on our website.

Human Evolution ICSE Class 10 Biology

Human Evolution ICSE Class 10 Biology

TOPIC-1
Human Evolution

Quick Review
➢ Salient Features of man
1. Bipedal gait
2. Erect posture
3. Grasping hands
4. Large cranium and brain
6. Social organization
7. Speech
8. Steep and high brow
9. Distinct chin

➢ Evolutionary Trends
1. The main trend of evolution of man is that he left his arboreal life and descend to the ground.
2. Opposable digits are required for grasping the branches. Due to terrestrial life opposability of toes was absent.
3. Upright posture is made possible by a lumber curve in the vertebral column.
4. Development of bipedal locomotion.
5. Development of chin.
6. Increase in size and complexity of brain.
7. Development of intelligence.
➢ The average fossils are placed in this order
➢ Apes Ape man Primitive man Modern man
➢ Australopithecus was a missing link between man and ape. It was an ape man.
➢ Erect posture, bipedal gait, forward position of foramen magnum, dentition etc. are of human characters in it.
➢ Small cranium and brain, large teeth, absence of chin, projection of eye brow over eyes etc. are ape characters of it.
➢ Homo habilis lived in Africa about 2 million years ago.
➢ It had bipedal locomotion, moved erect and was omnivorous. It had about 700 c.c. cranial capacity. The teeth were like modern man.
➢ He also led community life in caves and greatly cared for the young ones.
➢ Home erectus appeared about 1.7 million years ago in middle Pleistocene. H. erectus evolved from homo habilis. The chief characters of H. erectus are
(i) Bipedal gait
(ii) Taller than Australopithecus
(iii) Cranium is intermediate between Australopithecus and modern man.
(iv) He had protruding jaws, projecting brow ridges and small canines and large molar teeth.
(v) Chin was absent.
(vi) Used fire and tools and lived in caves.

➢ Neanderthal man were first obtained from Neander valley in Germany from the late Pleistocene. The chief characters are
(i) Shorter than modern man.
(ii) Eyebrows are protruding
(iii) No chin
(iv) Teeth were large.
(v) Cranial capacity was 1400 c.c.
➢ Cro-Magnon man emerged about 34000 years ago in Holocene epoch.
➢ The Cro-Magnon man had, like us, about 1.8 meter tall, well built body. It had elevated nose, broad and arched forehead, moderate brow ridges, strong jaw with man like dentition and well developed chin.
➢ Its cranial capacity was about 1650 c.c.
➢ Homo sapiens sapiens appeared about 25000 years ago in Holocene epoch and start spreading all over the world about 10,000 years ago.
➢ Morphologically, the transition is marked merely by a slight raising of skull cap, thinning of skull bones, a slight reduction in cranial capacity ( 1300 – 1600 c.c. ), and formation of four curves in the vertebral column.

Human Evolution ICSE Class 10 Biology
TOPIC-2
Theories of Evolution

➢ The term evolution literally denotes the process of continuous change. It is said that nothing is constant except the constant change.
➢ Abiogenesis is the origin of life from non-living matter & Biogenesis is the origin life from pre-existing life.
➢ Changes in relation to living organisms ( Plants and animals ) are described as organic evolution.
➢ Changes that occur in non living things ( topography of earth, chemical compounds of universe etc ) are described as inorganic evolution or cosmic evolution.
➢ Chemical evolution means formation of diverse organic molecules from inorganic constituents.
➢ The most convincing definition of organic evolution in words of Darwin himself is the descent with modification.
➢ Lamarck was the first biologist to postulate the theory of evolution in a convincing and scientific manner.
➢ His theory was mainly based on the following points.
(i) As far as the environment remains unchanged, the organism also become unchanged.
(ii) If there is any change in the environment, it creates new habits or change in the requirements of individuals.
(iii) As result, the organisms acquire certain modifications in the body, which are suitable to face the changed environments.

➢ Use and Disuse
(i) The modifications that occur due to influence of environment may be useful or not continuously to that organism.
(ii) The useful organs become stronger and better developed (use), while those which are not used become weak and ultimately disappear (disuse).
(iii) The characters which are developed due to use and disuse and influence of environment are called acquired characters.

➢ Examples cited by Lamarck to support his theory
(i) The short necked antelope like ancestors of giraffe happened to live in barren place and began to feed on leaves of trees. Therefore to reach the leaves of trees they began stretching the neck and fore limbs continuously. As a result, neck and forelimbs gradually increase in size (due to use) and that characters are transmitted to generation after generation. As a result, present day giraffe is formed.
(ii) Similarly, the muscles of pinna, vermiform appendix and wisdom teeth in man are the examples of vestigial organs which are reduced due to disuse of these organs whereas, in other mammals these organs are well developed due to continuous use.

➢ Darwinism and Theory of Natural Selection
➢ Darwin (1859) after extensive study of nature for about 20 years, published his monumental work on the origin of species by Natural Selection in the book ‘ Origin of Species’. The sea voyage of Charles Darwin in H.M.S Beagle round the world explored the ideas of common ancestor, natural selection, reproduction fitness, variations, adaptive radiation, etc. He suggested that the animals always adapt themselves to their environment and to ensure the continuity of their race, they reproduce their own kinds. Those who fail to adapt themselves to their environment perish in due course and the fittest survive ruling over the land. Thus there always prevails some sort of selection in nature and this is known as Natural Selection.
➢ Darwin finches, Australian marsupials are the example of adaptive radiation in their respective habitats. Branching descent & natural selection are the two key concepts of Darwinism theory of evolution.
➢ Industrial Melanism was worked out by Fisher Ford and Kettlewell on peppered moth Biston betularia. Nonmelanic or light coloured moths were common in Great Britain. In 1845,, one black or melanic moth appeared in Manchester – the industrial town. By 1848 the black variety of carbonaria formed 99% of moth population.
➢ In the black scooty atmosphere the melanic variety of moths was more successful because it could not be detected by the predatory birds. The nonmelanic or light coloured moths were at a disadvantage because in the soot covered area, these were easily visible to predatory birds.
➢ The change in gene, genotype and phenotype frequencies corresponds to spreading of industries.

Need for the regulation of body activities

Question. Endocrine glands secrete certain chemicals known as hormones.
Answer. Chemical substance secreted by endocrine or ductless gland and poured into blood to act on target organs or cells.

Question. Briefly explain the term hormone.
Answer. Hormone is a secretion from some glandular part of the body, which is poured directly into blood and which acts on the target organs or cells of the same individual, bringing about coordination between distant parts of the body.
Note Hormones are produced in very small quantities and are biologically very active.

Question. differentiate between hormonal control and nervous control.
Answer.

Hormonal control	Nervous control
1. Usually slow.	1. Immediate or Rapid.
2. Transmitted chemically through blood.	2. Transmitted electrochemically through the nerve fibres and chemically across synapses
3. Affects different organs (widespread in body).	3. Affects only the particular muscles or the gland (local).
4. Effect is short term or long-lasting.	4. Effect only short-lived.
5. Can affect growth.	5. Cannot affect growth.
6. Can bring about specific chemical changes and regulates metabolism.	6. Does not influence chemical changes and cannot regulate metabolism.
7. Cannot be modified by learning from previous experience.	7. Can be modified to some extent by learning from previous experience.

General properties of hormones.

Fill in the blanks by selecting the appropriate alternative from those given in brackets.

Question. Regulation of activities inside the body are brought about by …………….. and …………….. systems. (nervous/digestive/ endocrine)

Question. Hormones are secreted directly into the …………….. (organs/lymph/blood)

Question. Chemically, some hormones are …………….. some steroids, some …………….. (proteins/amines/carbohydrates)

Question. Both …………….. or deficiency of hormones lead to serious consequences. (excess/absence)

Question. Hormones produced in one species usually show …………….. influence in other species. (similar/different)

Question. Give the characteristics of hormones pertaining to
(i) Site of action. (ii) Chemical nature. (iii) Manner of transportation.
Answer. (i) They act on target organs or cells usually away from their source.
(ii) Chemically, some hormones are peptides (proteins such as insulin) which are water soluble, some are amines (derived from amino acids such as adrenaline) again water-soluble and some are steroids (derived from cholesterol such as testosterone) which are lipid-soluble.
(iii) Hormones are secreted from their source (an endocrine gland) directly into the blood.

Endocrine glands.

Question. Given below is an outline of the human body showing the important glands.
(i) Name the glands marked A to E.
(ii) Name the hormone secreted by B.
Give one important function of this hormone.
(iii) Name the endocrine cells present in part C.
(iv) Name the hormone secreted by part D.
Give one important function of this hormone.

Answer. (i) Different glands labelled from A to E are
A — Pituitary gland. B — Thyroid gland. C — Pancreas. D — Adrenal gland. E — Ovary.
(ii) The hormone secreted by part ‘B’ is thyroxine.
Function: It helps in regulating the normal basal metabolism of body.
(iii) The endocrine cells present in part ‘C’ are islets of Langerhans
(iv) The hormone secreted by part ‘D’ is adrenaline.
Function: It prepares body for any emergency situation.

Question. state the exact location of adrenal glands and also mention its various parts?
Answer. The adrenal glands are like caps on the top of each kidney (ad: near, renal: kidney). Each adrenal gland consists of two parts:
(i) a central medulla and
(ii) a peripheral cortex.

Question. Sketch and label the structure of adrenal gland.
Answer.

Question. Name the hormone produced by adrenal medulla. Write its function.
Answer. Adrenal medulla secretes adrenaline (also called epinephrine and noradrenaline). Adrenaline is a hormone, which prepares the body to meet any emergency situation. for ‘’Fight” i.e. to face danger or for “flight”, to run away from it. Extra energy and strength is provided to the body in that situation.

Question. write two conditions in which adrenal glands produce lot of adrenaline.
Answer. When excited or angry, our adrenals produce a lot of adrenaline.

Question. Give reason. Adrenaline is often described as the emergency hormone.
Answer. ⇒ It increases heart beat accompanied by an increase in blood pressure.
⇒ It increases blood supply to the muscles while decreasing it to skin and visceral organs.
⇒ More glucose is released into the blood by the liver (like putting more fuel into the engine). [The final dash to win a race is under the influence of adrenaline].