B2 - Evolution and Pollution

Question 1

Define evolution

Answer 1

The gradual change of an organism over time.

Question 2

What are the four main steps in natural selection?

Answer 2

1. Large populations
   • Most species produce lots of offspring. This should cause a massive population growth for every species.
2. Survival
   • Not all of the organisms in a population survive and reproduce. If all the organisms die, the species becomes extinct.
   • Their survival is affected by changes in the environment. Some die from disease. Some starve. Some are eaten by predators. Some cannot find a mate.
3. The fittest
   • In any population there is a lot of variation, caused by chance mutations in genes. Some of the variations will be an advantage. Animals without the advantage die.
4. Passing on the advantage
   • The surviving animals are the only ones that reproduce.
   • Their offspring inherit the advantage.
   • Over many generations the number of animals with the advantage increases.
   • The result is that the species has changed to become one with the advantage.

Question 3

How can two new species form from one species?

Answer 3

1. The populations become separated by some kind of barrier.
2. Over time, each separated group of the population evolves differently in different conditions on each side of the barrier. The longer they are separated, the more different they become.
3. The two sub-populations have changed so much that they can no longer interbreed. They have formed separate but closely related species.

Question 4

How did Darwin collect his evidence for evolution?

Answer 4

Charles Darwin travelled the world on the ship HMS Beagle. He made notes on the different types of plants and animals he saw. This evidence helped him develop his ideas on evolution – how the different species might have arisen. His ideas explained all the observations he made while travelling.

Question 5

What was Jean Lamarck’s theory on evolution and why was it rejected?

Answer 5

• In a giraffe population, some giraffes want to feed off
the leaves high on a tree.
• The giraffes stretch their necks, becoming more
successful.
• They pass their longer neck on to their offspring.
Evidence shows that the only changes in organisms that can be passed on to offspring are changes in genes, not changes acquired during the organism’s lifetime. Lamarck’s theory cannot be accepted because it does not explain the evidence of inheritance by genes.

Question 6

Define the term living fossil.

Answer 6

some organisms that have not changed over millions of years. This is possibly because their environment has not changed.

Question 7

What are the effects of our large and increasing population?

Answer 7

• There is a shortage of food in some countries.
• More land is being used for building and farming.
• More pollution is being produced.
• The world’s resources (such as fossil fuels and minerals)
are being used up too fast.

Question 8

How do humans affect agriculture and towns/ industries ?

Answer 8

Agriculture :
• use of fertiliser
• use of pesticides
• loss of habitat
• deforestation
• monoculture
• animal waste

Towns / Industries :
• loss of habitat
• quarrying and extraction of raw materials
• dumping of wastes
• production of toxic chemicals
• sewage

Question 9

Where does sulfur dioxide and nitrogen oxides come from and what are its effects on the environment?

Answer 9

Source - burning fossil fuels

Effects : dissolves in rain to form acid rain:
• damages plant leaves
• acidifies lakes = dead fish
• changes minerals available in water supplies
• causes bronchitis
- erodes limestone

Question 10

Where does carbon dioxide come from and what are its effects on the environment?

Answer 10

Source - burning fossil fuels

Effects :
- Dissolves in rain to form acid rain (same effects as other card).
A greenhouse gas which keeps more heat in the atmosphere, leading to global warming.

Question 11

Where do CFCs come from and what are its effects on the environment?

Answer 11

Source - aerosols and refrigerator coolants

Effects - Destroy the ozone layer in the upper atmosphere, allowing more ultraviolet radiation through and contributing to skin cancers.

Question 12

Describe two water pollutants and their effects on the environment.

Answer 12

Untreated sewage:

• Bacteria can cause disease, e.g. typhoid and cholera.
• Nitrates in the water kill fish.

Detergents :
- Kill organisms in the water and affect food chains.