Ch17: Variation & Evolution

Question 1

What is taxonomy?

Answer 1

The science of classifying organisms

Question 2

What is a species?

Answer 2

A group of similar organisms that are capable of naturally interbreeding with each other, but not with other such groups, to produce fertile offspring

Question 3

What is variation within species?

Answer 3

In a group of successfully interbreeding organisms, the individual members show different characteristics

Question 4

What are two types of variation and give examples

Answer 4

1. Acquired variation, e.g. ability to speak French or ride a bike
2. Inherited variation, e.g. ear shape

Question 5

Explain why sexual reproduction is responsible for most variations?

Answer 5

1. Independent assortment of chromosomes during meiosis
2. During meiosis, crossing over takes place (allows genes to be exchanged between chromosomes and produces combinations of genes inherited from parents)
3. At fertilisation, due to the random assortment of chromosomes in the egg and sperm, large range of variation is possible

Question 6

What is a mutation?

Answer 6

Spontaneous change in the amount or structure of DNA

-Any gene is affected
-Cells have enzymes to repair DNA damage, therefore few mutations survive)

-Mutation in a gene means the protein is no longer formed, now called recessive allele
-Many mutations produce no change in characteristics in diploid organisms as there are 2 copies of each gene

Question 7

Explain mutations in somatic cells

Answer 7

-May not be harmful
-Gene affected may not be active in the cell affected, e.g. skin cell that has mutation in saliva production gene
-Some somatic mutations are harmful if they cause an increase in rate of mitosis- may result in a tumour

Question 8

Explain mutations in gametes

Answer 8

-Often very serious
-Mutation can be inherited by the zygote and passed on to all cells in the child
-May cause genetic defects in the child or in following generations

Question 9

Describe beneficial mutations

Answer 9

-They produce a better protein than the original
-These mutations are a source of evolution

Question 10

What are causes of mutations?

Answer 10

-Spontaneous mutations occur when DNA doesn’t produce an exact copy of itself or doesn’t repair properly
-Mutagens, e.g. Ionising radiation, chemicals, some viruses

Question 11

What are the two types of mutations?

Answer 11

-Point/Gene mutations
-Chromosome mutations

Question 12

Explain gene mutations

Answer 12

-A change in a single pair of bases
-E.g. haemophilia, sickle cell anaemia (Causes clumping of blood and weakness, treatment- blood transfusion)

Question 13

Explain chromosome mutations

Answer 13

-A large change in the structure or number of one or more chromosomes
-E.g. Downs Syndrome

Question 14

What is evolution? Who is the father of evolution?

Answer 14

The way in which living things change genetically to produce new forms of life over long periods of time

Charles darwin

Question 15

What is Observation 1 and Conclusion 1 of Darwin’s Theory of Natural selection?

Answer 15

O1: Overbreeding, organisms produce large numbers of offspring

C1: There are too many organisms produced for the resources available

Question 16

What is Observation 2 and Conclusion 2 of Darwin’s Theory of Natural selection?

Answer 16

O: Population numbers remain constant once the environment cannot support anymore

C: There is competition for vital resources and weaker organisms die

Question 17

What is Observation 3 and Conclusion 3 of Darwin’s Theory of Natural selection?

Answer 17

O: Inherited variations occur in populations

C:
-Some organisms have variations so that they adapt better to their environment
-These variations are passed down to offspring
-Organisms with unfavourable variations will not survive to pass on their variations (survival of the fittest)

Question 18

What is natural selection?

Answer 18

The process by which those organisms with genetically controlled characteristics, that allow them to be well adapted to their environment, will survive and reproduce to pass on their genes to following

Question 19

What is speciation?

Answer 19

The production of new species as a result of evolution

Question 20

What evidence of evolution do we have?

Answer 20

Study of fossils

Fossils: the remains of something that lived a long time ago

Paleontology: the study of fossils

Question 21

Explain how fossils are evidence for evolution

Answer 21

-Can be aged through carbon-14 dating or by observing the depth in which they are found in soil or rock

-They show changes when compared to modern organisms
-Some fossils are extinct- they evolved into something else
-Some modern species have no fossil record- evolved from something else

-Modern fossils show increased complexity

Question 22

Explain the evolution of a horse

Answer 22

-Well documented fossil record- 60 millions years (many species-now extinct)