Evolution

Question 1

Variation

Answer 1

Differences between individuals. Can be interspecific: differences between individuals of different species; or intraspecific: different forms of a characteristic shown by members of the same species. Variation is important as it allows natural selection of individuals, resulting in adaptation and evolution of the species

Question 2

Continuous variation

Answer 2

• Significantly effected by environmental influences
• Quantitative
• Combined effect of many genes (polygenetic inheritance) with different alleles, each having a small effect
• Complete range of measurements from one extreme to another
• Plotted data shows a typical bell shaped normal distribution
• Data plotted as a frequency histogram
• Data is continuous

Question 3

Discontinuous variation

Answer 3

• None/very little environmental influences
• Qualitative
• Controlled by alleles of a single gene/small number of genes
• Feature can’t be measured across a complete range
• Individuals fall into distinct categories
• Data plotted as a bar chart
• Data is discrete/categoric

Question 4

Examples of continuous variation

Answer 4

Height, mass, length, IQ, skin colour, milk yield, width

Question 5

Examples of discontinuous variation

Answer 5

Blood group, gender, tongue rolling, attached/free ear lobes, colour of flower, tall/dwarf pea plants, antibiotic resistance in bateria, presence of flagella

Question 6

Causes of variation

Answer 6

Genetic: caused by differences between genes and the combinations of genes or alleles
Environmental: characteristics affected by the environment, e.g. weight, skin colour (tan).

Question 7

Behavioural adaptation

Answer 7

An aspect of the behaviour of an organism that helps it to survive the conditions it lives in, e.g. killer whales hunting in a herd

Question 8

Physiological adaptation

Answer 8

Or biochemical adaptation. Ensures correct functioning of cell processes, e.g. respiring anaerobically or aerobically in yeast, depending on environment. Also producing correct enzymes.

Question 9

Anatomical adaptation

Answer 9

Any structure that enhances the survival of an organism. E.g. flagellum, angler fish lure

Question 10

4 observations made by Darwin

Answer 10

• Offspring generally appear similar to their parents
• No two individuals are identical
• Organisms have the ability to produce large numbers of offspring
• Populations in nature tend to remain fairly stable in size

Question 11

Darwin’s conclusions

Answer 11

• Characteristics are passed on to the next generation (inheritance)
• There is a struggle for existence between members of a species
• Individuals with advantageous characteristics are among the few that survive

Question 12

Speciation

Answer 12

The formation of new species from a pre-existing one

Question 13

How evolution works

Answer 13

• Variation must occur before hand
• Once a variety exists, the environment will select the variations that give an advantage
• The individuals with the advantage will survive and reproduce, passing on the advantageous characteristic
• The next generation will be better adapted to survival

Question 14

Allopatric/sympatric speciation

Answer 14

Allopatric: most common. Where a geographical barrier isolates groups
Sympatric: where a barrier exists in a populations, e.g. behavioural (breeding times), physical isolation, ecological isolation