Evolution And Variation

Question 1

What are the causes of variation?

Answer 1

Characteristics may be purely genetic, where they are determined by the combinations of inherited from the parents.These will be determined from birth and cannot be changed.
Characteristics may be environmental where they are influenced by the conditions around the organism over its lifetime

Question 2

Identical twins

Answer 2

Identical’ twins are only genetically identical as they may have different experiences over their lives

Question 3

Continuous variation

Answer 3

these are numerical measurements with 2 extremes and a full range of intermediate values between them eg. height, length of leaves. (Height)

Question 4

Discontinuous variation

Answer 4

is where there are 2 or more distinct groups (categories) with no intermediate values eg. gender, blood group.

Question 5

Variation

Answer 5

This is the presence of variety, which refers to the differences between individuals
It will occur from one species to another, which is why they are classed as separate species in the first
Variation will also occur within the same species, as different individuals display different combinations of characteristics

Question 6

Explain why humans selectively breed plants an animals?

Answer 6

For 1000s of years, humans have been selectively breeding plants and animals in order to amplify these characteristics and suppress / eradicate undesirable ones

Question 6

Describe selective breeding as a type of sexual reproduction

Answer 6

Sexual reproduction mixes the genetic characteristics of 2 parents, producing variation amongst the offspring. Mixing the DNA produces variation.
The offspring with the most desirable characteristics are selected.
These animals / plants are then encouraged to breed, in order to pass on their desirable genes.
Their offspring are for those that have acquired the ‘best’ combination of characteristics and the process is repeated many times. All the less bad genes die of then you end up with and animal that has good genes. This could happen to humans but not artificially

Question 7

Explain the benefits of selective breeding in plants and animals

Answer 7

In farming, the main reason for selective breeding is to produce the most and tastiest food, maximising profits

Question 8

Explain the risks of selective breeding

Answer 8

This is risky, as if conditions change, eg. climate or a new disease, the whole species could become extinct as it is unable to evolve you have to have variation because if something changes you risk them all dying if disease occurs to one

Question 9

Describe Darwin’s theory of evolution by natural selection

Answer 9

1. Individual organisms within a particular species may show a wide range of phenotype because of differences in their genes
2. Individual with characteristic most suited to its environmental are more likely to survive to breed successfully
3. The genes that have enabled these individuals to survive are then passed on to the next generation

Question 10

Why was Darwin theory accepted?

Answer 10

1. He had evidence

2. It challenged the Theory of God created the world

Question 11

Describe the work of Alfred Russel Wallace on natural selection

Answer 11

His theory was similar to Darwin

Question 12

Describe the work of Lamarck

Answer 12

He thought that any changes that occur in an organism’s life would be passed on to the offspring
This meant that any feature used lots would. Develop more and anything not used would disappear
This was called the inheritance of acquired characteristics,commonly called ‘use it or lose it’. It’s an environmental cause not genetic

Question 13

Why was Lamarck theory wrong?

Answer 13

This mechanism was shown to be incorrect, as characteristics gained during a lifetime (environmental causes of variation) cannot be passed on
Only genetic characteristics can be inherited by the offspring, passed down through the sex cells