Evolution

Question 1

What is fossil

Answer 1

Fossil are the preserved remains and traces of ancient organisms.

Question 2

How does the fossil formed ?

Answer 2

• the fish dies. Its body sinks to the bottom of a lake. The soft part of the fish decay, leaving the hard parts like the skeleton. The skeleton then buried in sand and mud.
• After Million’s of years, the mud and sand become rock due to the great pressure of the upper part of the sediment. The minerals begin to deposit in the fish skeleton and turn it into a fossil
• the earth movement raises the rock above
• further earth movement or weathering exposes the fossil

Question 3

Suggest another way to preserve remains of organisms

Answer 3

• Small animals might get trapped in resins secreted by trees. After long time, resin turns into amber, preserving the animals inside.
• Organisms can also be preserved in ice.

Question 4

How a fossil record provides evidence for evolution

Answer 4

•The sequence of fossils in sedimentary rocks forms the fossil record.
-In sedimentary rocks, the lowest layer is the oldest rock containing the earliest fossils. eaniest
•The fossil record agrees with the theory of evolution that:
-life forms existing life forms arose from ore-existing life forms
-organisms became more diversified in structure and more complex
•estimate the age of fossils by radioisotope dating

Question 5

What are the limitations of using fossil records as evidence for evolution?

Answer 5

• There are missing links in fossil records.
• Soft-bodied organisms usually do not form fossils.
• The bodies of dead organisms may be eaten by other organisms or decay before fossilization
• The conditions in which the organisms died are not suitable for fossil formation.
• incomplete and may be damaged.
• Most fossils are Some fossils are located in inaccessible areas.

Question 6

Other than fossil records, what other evidence is there to support the theory of evolution?

Answer 6

• Homologous structures in certain species suggest that these species have evolved from a common ancestor.
• Comparative studies looking at the amino acid sequence in proteins and the base sequence of DNA between different species show that a higher degree of similarity is found in more closely related species.

Question 7

How does evolution take place?

Answer 7

• Charles Darwin put forward the theory of natural selection to explain how evolution takes place.
• The theory suggests that variations exist among individuals withina species. The individuals compete with one another for limited resources (i.e. struggle for survival). When the environment changes, individuals with favourable characters have a higher chance of survival and reproduction (i.e. survival of the fittest). They pass the favourable characters on to their offspring. Over many generations, the action of natural selection leads to the evolution of new species.

Question 8

Why does an insecticide become less effective in killing insect pests when the insecticide is used repeatedly over a long period of time?

Answer 8

• Genetic variations exist among insect pests in their resistance to the insecticide. When the insecticide is applied, the non-resistant insect pests have a higher chance of survival and reproduction.
• When the insecticide is used repeatedly, the proportion of the resistant insect pests in the population increases in subsequent generations. As a result, the insecticide becomes less effective in killing insect pests.

Question 9

Why are some bacteria becoming increasingly resistant to a certain antibiotic ?

Answer 9

• Genetic variations exist among bacteria in their resistance to a certain antibiotic. When the antibiotic is used, the antibiotic-resistant bacteria have a higher chance of survival and reproduction.
• With the indiscriminate use of the antibiotic, the proportion of the resistant bacteria in the population increases in subsequent generations.

Question 10

What is speciation?

Answer 10

Speciation is the process by which new species form.

Question 11

How does speciation occur?

Answer 11

A population separates into small groups. The groups are isolated from one another (e.g. by a physical barrier) so that they cannot interbreed. Each group may then evolve independently by natural selection. After many generations, genetic variations may accumulate to a point where individuals of different isolated groups can no longer interbreed to produce fertile offspring. The isolated groups become different species.