Evolution and Variation

Question 1

Variation:

Answer 1

the differences in characteristics between individuals in a population due to genes, the environment or a combination of both

Question 2

What does the genome influence in an organism?

Answer 2

the genome and its interaction with the environment influence the development of the phenotype of an organism

Question 3

Processes that lead to genetic variation:

Answer 3

meiosis
sexual reproduction
mutations

Question 4

Causes of variation:

Answer 4

Genotype
the genes they have inherited (genetic causes)
genes passed on from the parents in sex cells
combining of genes from mother and father creates genetic variation
identical twins have same genotype
lots of genetic variation in a population
Environmental causes - the conditions in which they have developed in
Combination of genes and the environment

Question 5

What is there within a population?

Answer 5

usually extensive variation within a population of a species

Question 6

What do variants arise from?

Answer 6

variants arise from mutations
most mutations have no effect on the phenotype
some influence phenotype
very few determine phenoytype

Question 7

When do mutations occur?

Answer 7

mutations occur continuously as it is the change in the DNA code.
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 8

Evolution:

Answer 8

the 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 9

What does the theory of evolution state?

Answer 9

the theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than 3 billion years ago

Question 10

How does evolution occur?

Answer 10

Variation in the phenotype (this can be caused by mutation)

Selection Pressure ( environmental pressure due to predators, pathogens, food availability, etc.)

The organisms with characteristics that are best suited to the environment e.g. more able to obtain food are more likely to survive and reproduce.

They pass on their successful Alleles/genes to their offspring.

This is repeated over many generations so that the frequency of the successful gene/allele in the population increases.

Over time more organisms in the population will have the successful gene and therefore phenotype.

Question 11

When are 2 new species formed?

Answer 11

if 2 populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed 2 new species - speciation

Question 12

Selective breeding / artificial selection:

Answer 12

the process by which humans breed plants and animals in order to produce offspring with particular genetic characteristics / certain desirable characteristic(s)

Question 13

How does selective breeding take place?

Answer 13

parents with desired characteristics are chosen from a mixed population
they are bred together
from the offspring those with the desired characteristic are bred together
this process is repeated many times and continues over many generations until all the offspring show the desired characteristic

Question 14

What characteristics are animals/plants selectively bred for?

Answer 14

disease resistance in food crops
animals which produce more meat or milk
domestic dogs with a gentle nature
large or unusual flowers

Question 15

What is a problem with selective breeding?

Answer 15

can lead to inbreeding where some breeds are particularly prone to disease or inherited defects
breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals
this results in the reduction of the gene pool - as the number of different alleles reduce as they mostly have the same alleles
also if the environment changes or there is a new disease, the species could become extinct as they all have the same genetic makeup - so the chance of a few organisms having a survival advantage and not dying is reduced

Question 16

What did Charles Darwin propose and what was it backed by?

Answer 16

Charles Darwin proposed the theory of evolution by natural selection
as a result of observations on a round the world expedition, backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils

Question 17

How and when did Charles Darwin publish his ideas?

Answer 17

Darwin published his idea in ‘On the Origin of Species’ in 1859
there was much controversy surrounding these revolutionary ideas

Question 18

What was Charles Darwin’s theory of evolution?

Answer 18

individual organisms within a particular species show a wide range of variation for a characteristic
variation exists within a species due to differences in their genes possibly as a result of mutations in DNA
individuals with characteristics most suited to the environment are more likely to survive to breed successfully
the genes/characteristics that have enables these individuals to survive are then passed on to the next generation (natural selection)
over many generations the frequency of alleles/genes for this advantageous characteristic increase within the population
individuals that are poorly adapted to their environment are less likely to survive and reproduce → this means that their genes are less likely to be passed on to the next generation

Question 19

Why was the theory of evolution by natural selection only gradually accepted?

Answer 19

the theory challenged the idea that God made all the animals and plants that live on Earth
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 20

What was Jean-Baptise Lamarck’s theory?

Answer 20

based mainly on the idea that changes that occur in an organism during its lifetime can be inherited
if an individual repeated an action, the characteristic that allowed it to do this would develop further

Question 21

How was Lamarck’s theory proven wrong?

Answer 21

know that in the vast majority of cases this type of inheritance cannot occur
his theory was proven wrong when it was understood that changes caused by the environment were not passed on in the sex cells

Question 22

Speciation:

Answer 22

the process of a new species developing through the selection of different alleles
this increases genetic variation until the new population cannot breed with those in the old population to produce fertile offspring

Question 23

What did Alfred Russel Wallace propose?

Answer 23

Alfred Russel Wallace 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

Question 24

How did Alfred Russel Wallace work?

Answer 24

Wallace worked worldwide gathering evidence for evolutionary theory - on his travels he had the idea that individuals who did not have the characteristics to help them survive a change would die out
Alfred Russel Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation

Question 25

What is Alfred Russel Wallace’s best known work?

Answer 25

best known for his work on warning coloration in animals and his theory of speciation

Question 26

Process of speciation:

Answer 26

Variation exists within a population as a result of genetic mutations
Alleles which provide a survival advantage are selected for through natural selection
Populations of a species can become isolated e.g. through geological barriers preventing them from breeding together
Habitat variation
Genetic variation in each population
Natural selection - different alleles may be advantageous in the new environment, leading to them being selected for so that the animals in the separate populations are better adaptâtes to survive and reproduce - pass on advantageous alleles
Over time the selection of different alleles will increase the genetic variation between the 2 populations
When they are no longer able to breed together to produce fertile offspring a new species has formed

Question 27

Causes for new species to arise:

Answer 27

genetic variation - each population has a wide range of alleles that can control their characteristics
natural selection - the alleles which help an organism to survive are selected in each population
speciation- the populations become extremely varied and successful interbreeding cannot happen anymore
isolation

Question 28

How can new species arise through isolation?

Answer 28

two populations of a species can become geographically separated because of the environment
isolation can prevent interbreeding and the combination of genes within a species
different mutations can take place in the isolated groups and create different phenotypes within a particular location
over time species may evolve to be different to each other, and they will not be able to interbreed

Question 29

What is now widely accepted?

Answer 29

the theory of evolution by natural selection is now widely accepted

Question 30

Evidence for the theory of evolution:

Answer 30

has been show that characteristics are passed on to offspring in genes
fossil record - the remains of organisms from many years ago which are found in rocks
antibiotic resistance in bacteria - the selection pressure of antibiotics leads to advantageous mutations being selected for in bacteria populations so they are no longer killed when exposed to antibiotics