Kerala Syllabus Class 10 Biology Chapter 2. 'Paths of Evolution' Textbook Solutions

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1. Two illustrations related to human evolution are given below. Based on the theory of natural selection, find out the correct one and explain the reason.

Ans:

Illustration A is the correct one. Illustration A accurately depicts that humans and monkeys share a common ancestor, from which both lineages diverged and evolved independently. This aligns with the theory of evolution, which states that different species can evolve from a shared ancestral species over time. Illustration B incorrectly suggests that humans evolved directly from monkeys, which is a common misconception about human evolution.

2. Although dolphins have a larger brain than that of humans, the level of thinking, language skills, and social relationships are higher in humans.

Evaluate this statement based on the following indicators.

• Difference in the structure of the brain

• Influence of natural selection

Ans:

While dolphins may have larger brains in absolute terms, the size alone doesn't directly equate to intelligence. The structure and complexity of the brain is more important. Humans have a more developed neocortex compared to that of dolphins. Advanced mental processes such as thinking, decision-making, learning, recalling, etc. are made possible with the help of the synapses of neocortex.

3. Redraw the figure of the neuron and label the following parts by writing their names.

(a) The part of the neuron that receives impulses from the adjacent neuron

(b) Part that contains a neurotransmitter

(c) Part that acts as an insulator

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4. Darwin failed to explain the reasons for variation even though he argued that variations occur continuously in organisms. Evaluate this statement based on the findings of Neo Darwinism.

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Darwin noted that organisms within a population exhibit variations, yet he did not grasp the genetic foundations of these differences. He lacked the knowledge of genetics, which is crucial to understanding how variations are passed on from generation to generation. Neo-Darwinism addresses this gap by explaining that random mutations in DNA are the primary source of these variations. Such mutations can introduce new traits into a population, which are then subject to the processes of natural selection.

5. Observe the illustration and answer the questions.

(a) Identify the nerves A and B.

(b) Are messages being exchanged between A and B? Explain.

Ans:

a) A - Motor nerve

    B - Sensory nerve

b) Yes, messages are exchanged between sensory and motor nerves, but not directly. Sensory neurons transmit information from the body to the central nervous system, while motor neurons carry signals from the central nervous system to different body parts. Interneurons within the central nervous system act as intermediaries, relaying information between sensory and motor neurons. 

6. A table that includes the parts of spinal cord and their functions is given below. Arrange column B appropriately in accordance with column A of the table.

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7. Based on the information obtained from fossils, some human ancestors and their characteristics are given below. Find out the one which is arranged correctly from the given answers.

(A) Homo habilis                       (i) buried dead bodies

(B) Homo neanderthalensis    (ii) able to stand upright on two legs

(C) Astralopithecus                 (iii) made tools with stones using their hands

(D) Homo erectus                    (iv) The skeletal structure confirms bipedalism

(a) A : i, B : ii, C : iii, D : iv      (b) A : iii, B : i, C : iv, D : ii

(c) A : iii, B : iv, C : ii, D : i      (d) A : iv, B : i, C : iii, D : ii

Ans: (b) A : iii, B : i, C : iv, D : ii

8. Examine the information mentioned in the boxes labelled as P, Q, R, S.

Identify the part of the brain associated with them and choose the correct answer.

(a) P – Medulla oblongata Q – Pons R – Hypothalamus S – Thalamus

(b) P – Pons Q – Hypothalamus R – Medulla oblongata S – Cerebrum

(c) P – Hypothalamus Q – Cerebrum R – Thalamus S – Pons

(d) P – Thalamus Q – Cerebrum R – Hypothalamus S – Medulla oblongata

Ans: (c) P – Hypothalamus Q – Cerebrum R – Thalamus S – Pons

9. Complete the table by including the following in appropriate columns.

• Only long necked giraffes survive

• Use and Disuse

• Natural selection

• Variations acquired in the life span

• Through continuous use, giraffe's neck elongates

• Inheritance of variations

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