Lesson 2 - Darwin's Theory of Naturral Selection

Question 1

ANALOGOUS STRUCTURES

Answer 1

Perform similar functions. Structure and
developmental pattern are quite different.

Analogous structures: Structures in organisms that look similar or have similar functions, but don’t have a shared ancestral source.

Other Example: Wings of a bird and butterfly

Question 2

PROBLEMS WITH CLASSIFICATION SYSTEM

Answer 2

Sometimes, due to convergent evolution, organisms that are quite different from one another have similar structures.

Convergent Evolution
- Unrelated species become increasingly similar looking due to similar pressures in the environment
- Certain similar characteristics are favoured

Question 3

EVOLUTION

Answer 3

The processes that have transformed life on earth from its earliest forms to the vast diversity that characterizes it today.

A change in the genes

Question 4

OLD THEORIES OF EVOLUTION (Jean Baptiste Lamarck)

Answer 4

Jean Baptiste Lamarck (early 1800’s)
proposed:
- “The inheritance of acquired
characteristics”

He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

This theory has no genetic basis

“habit modifies form”

“use vs. disuse”

In ONE generation, all organisms in the
population display the acquired
characteristic

Question 5

CHARLES DARWIN

Answer 5

Influenced by Charles Lyell who published “Principles of Geology”

This publication led Darwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.

Darwin set sail on the H.M.S. Beagle
(1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals.

On the Galapagos Islands, Darwin observed
species that lived nowhere else in the world.

These observations led Darwin to write a
book.

Wrote in 1859:
“On the Origin of Species by Means of Natural Selection”

Two main points:

1.
Species were not created in their present
form, but evolved from ancestral species.

2.
Proposed a mechanism for evolution:
NATURAL SELECTION

Question 6

NATURAL SELECTION

Answer 6

Individuals with favorable traits are more likely to leave more offspring better suited for their environment.

Example:
English peppered moth (Biston betularia)
- Grey vs. black colour

1. Struggle for Existence – competition among
   organisms to survive
2. Variation – improves the individual’s
   chance of survival
3. Role of the Environment – adapt to their
   environment to avoid predators.

“Fitness” of an individual as its ability to survive and reproduce in its specific environment.

Darwin used the term “survival of the fittest” as a synonym for natural selection.

Question 7

ARTIFICIAL SELECTION

Answer 7

The selective breeding of domesticated plants and animals by man.

Question:
- What’s the ancestor of the domesticated
dog?

Answer: WOLF