b14/15 - variation, evolution and genetics

Question 1

what are species?

Answer 1

animals that are similar enough to breed together successfully

Question 2

what is variation?

Answer 2

the existence of variety and differences within and between species - caused by genetic mutation

Question 3

what are the two different types of variation?

Answer 3

continuous and discontinuous

Question 4

what is continuous variation?

Answer 4

• qualitative
• the full range of variables between 2 extreme values
• height, weight, length
• normally presented as a bell-curved shape

Question 5

what is discontinuous variation?

Answer 5

• aka discrete variables
• variables assigned to clear, distinct groups
• blood group, sex
• usually presented as a bar graph

Question 6

what does variation in a species rely on?

Answer 6

• relies upon mutations within a species
• variation is acted upon by selection pressure (what makes it more likely to survive)
• only the fittest (have most favourable characteristics) will survive to breed → evolution via natural selection

Question 7

what is genetic variation?

Answer 7

• every person on earth has their own genetic make up (unless they are a twin)
• a few traits are determined by a single allele eg, blood group and some inherited diseases
• most of our genes are controlled by more than one allele
• variation exists as a result of genetic mutations resulting in changes or loss of proteins

Question 8

what is environmental variation?

Answer 8

differences between organisms caused by environmental factors eg. language spoken, accent

Question 9

what could cause a difference between genetically identical hydrangeas?

Answer 9

• intake of mineral ions; magnesium and nitrate
• soil pH
• temperature/exposure to sunlight

Question 10

what could cause genetically identical twins to be different?

Answer 10

• exercise
• diet
• intake of substances (alcohol, drugs, tobacco)

Question 11

what is inherited variation?

Answer 11

differences between organisms passed to their offspring by their parents in reproduction eg. eye colour, natural hair, blood type

Question 12

what is darwin’s theory of evolution by natural selection?

Answer 12

1) individual organisms in a particular species tend to show a wide variation for each characteristic
2) reproduction always gives more offspring than the environment can support.
- the organisms with the inherited characteristic most suited are more likely to survive and breed (survival of the fittest!)
3) when they breed. they pass on the characteristics that have enabled them to survive to the next generation

Question 13

what is natural selection?

Answer 13

1) variation exists as a result of genetic mutations #
2) some are better adapted to survive in a certain environment
3) they reporduce
4) their alleles are passed onto their offspring
5) when this process happens over many generations, it results in evolution

Question 14

what was lamarck’s theory?

Answer 14

based mainly on the idea that changes that occur in an organism during its lifetime can be inherited
- a characteristic that is used frequently by an organism becomes better and stronger, whereas a characteristic that isn’t used gradually disappears
- the beneficial characteristics that are used frequently (and are improved as a result) are passed to offspring

Question 15

what are three causes of variation in a population?

Answer 15

• genes
• environment
• a combination of both