The evidence for natural selection 4.3.5

Question 1

What idea did Darwin and Wallace have?

Answer 1

• The idea that one species might evolve from another over time was not new, but Darwin proposed a mechanism for this process
• His proposed mechanism was natural selection

Question 2

Define natural selection

Answer 2

Is the mechanism by which organisms change over time as they adapt to changing environments

Question 3

What observations did Darwin, which then led to the proposed mechanism of natural selection?

Answer 3

1. Offspring generally appear similar to their parents
2. No two individuals are identical
3. Organisms have the ability to produce large numbers of offspring
4. Population numbers remain fairly constant despite overpopulation
   He realised that variation was the key - and when overpopulation occurs there is competition for resources.
   He then came to the realisation that some offspring are better adapted than others.

Question 4

What is overproduction?

Answer 4

When more offspring are produced than can survive.

Question 5

What happens once natural selection occurs in an organism?

Answer 5

The better adapted individuals obtain enough food and survive long enough to reproduce - their characteristics are then passed on to the next generation.

Question 6

What are Darwin’s conclusions?

Answer 6

• There is a struggle to survive
• Better adapted individuals survive and pass on their characteristics
• Over time, a number of changes may give rise to a new species

Question 7

Name 2 pieces of evidence for evolution

Answer 7

1. Fossil evidence
2. Biological molecules

Question 8

What is fossil evidence?

Answer 8

• In the past the world was inhabited by species that were different from those present today
• Old species have died out
• The new species that have appeared are often similar to the older ones found in the same place

Question 9

What are the 5 stages of fossilisation?

Answer 9

1. An animal dies and its body sinks to the sea floor. The soft parts of the animal rot away and the skeleton gets buried by mud and sand
2. The sediment surrounding the skeleton get thicker as new layers form above. The pressure from above turns the layers to hard rock
3. The skeleton dissolves, leaving a cavity and a mould the shape of the skeleton is formed
4. Water rich in minerals fills the cavity, The minerals crystallise inside the mould and a cast is formed
5. Millions of years later the rock surrounding the skeleton rises to the Earth’s surface

Question 10

What is comparative anatomy

Answer 10

• Similar underlying structure, even though may appear different and have different functions.
  This is a way of classifying