Topic 14

Question 1

Variation definition

Answer 1

differences in the characteristics of individuals in a population

Question 2

Variation may be due to differences in:

Answer 2

The genes they have inherited (genetic causes)
The conditions in which they have developed (environmental causes)
A combination of genes and the environment

Question 3

There is usually extensive genetic variation within a population of a species
Variants arise from:

Answer 3

mutations

Question 4

Mutations
how much they occur?
how they affect phenotype?

Answer 4

occur continuously: most mutations have no effect on the phenotype, some influence phenotype, very few determine phenotype
Very rarely a mutation will lead to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species

Question 5

Evolution

Answer 5

a change in the inherited characteristics of a population over time through a process of natural selection, which may result in the formation of a new species

Question 6

The theory of evolution by natural selection states that

Answer 6

all species of living things have evolved from simple life forms that first developed more than three billion years ago

Question 7

Explain how evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment:

Answer 7

Individual organisms within a particular species may show a wide range of phenotype variation because of differences in their genes
Individuals with characteristics most suited to the environment are more likely to survive and breed successfully
The genes that have enabled these individuals to survive are then passed on to the next generation

Question 8

how are two new species formed

Answer 8

If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring

Question 9

The theory of evolution by natural selection developed over time and from information gathered by many scientists:

Answer 9

Charles Darwin proposed the theory of evolution based upon observations from his round the world expedition, backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils.
Darwin published his ideas in “On the origin of species (1859)”. There was much controversy surrounding these revolutionary new ideas.

Question 10

The theory of evolution by natural selection was only gradually accepted because:

Answer 10

The theory challenged the idea that God made all animals and plants that live on EarthThe theory of evolution by natural selection developed over time and from information gathered by many scientists:
There was insufficient evidence at the time the theory was published to convince many scientists
The mechanism of inheritance and variation was not known until 50 years after the theory was published

Question 11

Jean-Baptiste Lamarck theory

Answer 11

based mainly on the idea that changes that occur in an organism during its lifetime can be inherited. We now know that in the vast majority of cases this type of inheritance cannot occur.

Question 12

Bacteria can evolve rapidly because they

Why might this be a problem /what problems does it cause?

Answer 12

at a fast rate

Mutations of bacterial pathogens produce new strains.
Some strains might be resistant to antibiotics, so are not killed.
Resistant strains survive and reproduce, so the population of the resistant strain rises.
The resistant strain spreads because people are not immune to it and there is no effective treatment.
MRSA is resistant to antibiotics

Question 13

what can be done to reduce the rate of development of antibiotic resistant strains:

Why is this needed:

Answer 13

Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
The agricultural use of antibiotics should be restricted

The development of new antibiotics is costly and slow. It is unlikely to keep up with the emergence of new resistant strains.

Question 14

Fossils are

Answer 14

the ‘remains’ of organisms from millions of years ago, which are found in rocks.

Question 15

Fossils may be formed:

Answer 15

From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
When parts of the organism are replaced by minerals as they decay
As preserved traces of organisms, such as footprints, burrows and rootlet traces

Question 16

why cannot scientists be certain about how life began on Earth:

Answer 16

Many early forms of life were soft-bodied, which mean that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.

Question 17

Extinctions occur when

Answer 17

there are no remaining individuals of a species still alive.

Question 18

Describe factors which may contribute to the extinction of a species:

Answer 18

Changes to the environment over geological time
New predators
New diseases
New, more successful, competitors
A single catastrophic event eg. massive volcanic eruptions or collisions with asteroids

Question 19

Alfred Russel Wallace

Answer 19

independently proposed the theory of evolution by natural selection. He published joint writings with Darwin in 1858 which prompted Darwin to publish “On the origin of species (1859)” the following year.
Wallace worked worldwide gathering evidence for evolutionary theory. He is best known for his work on warning colouration in animals and his theory of speciation.
Alfred Wallace did much pioneering work on speciation but more evidence over time has lead to our current understanding of the theory of speciation.

Question 20

New species arise as a result of:

Answer 20

Isolation of populations
Genetic variation between populations
Natural selection operating differently on the two populations
Speciation: the populations become so different that successful interbreeding is no longer possible

Question 21

Selective breeding (artificial selection) is the process by which

Answer 21

umans breed plants and animals for particular genetic characteristics. Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals.

Question 22

Selective breeding involves:

Answer 22

Choosing parents with the desired characteristic from a mixed population
Breeding selected parents together
Selecting offspring that have inherited the desired characteristic and breeding them together
Repeating over many generations until all offspring show the desired characteristic

Question 23

The characteristic can be chosen for usefulness or appearance:

Answer 23

Disease resistance in food crops
Animals which produce more meat or milk
Domestic dogs with a more gentle nature
Large or unusual flowers

Question 24

Selective breeding can lead to

Answer 24

‘inbreeding’ where some breeds are particularly prone to disease or inherited defects eg. some breeds of dog suffer frequent defects

Question 25

Genetic engineering is a process which involves

Answer 25

modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

Question 26

Enzymes use in genetic engineering
vectors then
why what

Answer 26

are used to isolate the required gene; this gene is inserted into a vector, usually a plasmid or virus
The vector is used to insert the gene into the required cells
Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so they develop with desired characteristics

Question 27

Genetically modified (GM)

Answer 27

crops generally show increased yields because of characteristics chosen eg. larger fruits / disease resistance / herbicide resistance

Question 28

Bacterial cells have been

Answer 28

genetically engineered to produce useful substances such as human insulin to treat diabetes

Question 29

Genetic engineering has potential benefits and risks in agriculture and medicine, and some people have objections:

Answer 29

Benefits:
Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders
Risks:
Concerns about GM crops include the effect on populations of wild flowers and insects
Some people feel the effects of eating GM crops on human health have not been fully explored

Question 30

Plant cloning:

Answer 30

Tissue culture (using small groups of cells from part of a plant to grow new plants.) Importance for preserving rare plant species or commercially in nurseries
Cuttings (older but simpler method used by gardeners to produce many identical new plants from a parent plant)

Question 31

Animal cloning:

Answer 31

Embryo transplants (splitting apart cells from developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers)
Adult cell cloning
The nucleus is removed from an unfertilised egg cell
The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
An electric shock stimulates the egg cell to divide to form an embryo
These embryo cells contain the same genetic information as the adult skin cell
When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

Question 32

Adult cell cloning

Answer 32

The nucleus is removed from an unfertilised egg cell
The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
An electric shock stimulates the egg cell to divide to form an embryo
These embryo cells contain the same genetic information as the adult skin cell
When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development