A2 OCR Biology - F215 - Evolution

HideShow resource information
  • Created by: Jess
  • Created on: 14-04-14 20:10
Define variation
The differences that exist between individuals - each individual is unique
1 of 62
Describe the characterstics of continuous variation
No distinct categories, often influenced by many genes (polygenic)
2 of 62
Give 2 examples of continuous variation
Height or mass
3 of 62
Give 2 examples of discontinuous variation
Gender or blood group
4 of 62
Describe the characterstics of discontinuous variation
Falls into 2 or more distinct categories, no intermediates, usually only influenced by one gene (or a small number of genes) (monogenic),
5 of 62
What is variation affected by?
Genes, the environment, genes and the environment together
6 of 62
Fill in the blank: Individuals of the same species have the same genes but different ______ __ ____
Versions of them - ie. alleles
7 of 62
What does it mean if something is influenced by many genes?
It is polygenic
8 of 62
Give 2 examples of variation caused solely by the environment
Accent or whether you have pierced ears
9 of 62
Give 2 examples of variation caused by genes and the environment
Human body mass - partially genetic but also affected by factors like diet and exercise (continuous) / Height of pea plants - tall or dwarf (discontinuous) but exact height varies because of light intensity/water availablility etc. (continuous)
10 of 62
Variation caused by genes and the environment is normally of what type (discontinuous or continuous)?
Continuous
11 of 62
Define gene pool
The complete range of alleles present in a population
12 of 62
How are most new alleles often generated?
By mutations
13 of 62
Define allele frequency
How often an allele occurs in a population
14 of 62
What unit is allele frequency normally given in?
As a percentage or decimal
15 of 62
What is evolution?
The change in the frequency of an allele in a populatino over time
16 of 62
Name three things that cause natural selection
Predation, disease, competition
17 of 62
Describe the process of natural selection
Some individuals better adapted than others, increased chances of survival, more likely to survive and reproduce, pass on their beneficial allele, greater proportion of next generation inherits the beneficial allele so allele frequency increases
18 of 62
What are the names of the 2 types of selection?
Stabilising and directional
19 of 62
Describe the process of stabilising selection
Environment isn't changing much, individuals with characteristics towards the middle of the range are more likely to survive
20 of 62
What is the (final) effect of stabilising selection?
There is a reduced rance of possible phenotypes and most individuals have middle-of-the-range characteristics
21 of 62
Describe the process of directional selection
Change in the environment, individuals with an extreme type of characteristic are more likely to survive and reproduce
22 of 62
What is the (final) effect of directional selection?
Most individuals have extreme characteristics on one end of the spectrum
23 of 62
Give an example of stabilising selection
Mammal's fur in a stable climate - those with fur of an average length survive
24 of 62
Give an example of directional selection
Environment becomes really cold, mammal's with long fur find it easier to maintain the right body temperature - those with longer fur survive
25 of 62
What are the 2 ways by which evolution occurs?
Natural selection and genetic drift
26 of 62
Define genetic drift
When evolution occurs because chance dictates which allele is passed on more often again and again, so the allele becomes more common in the population
27 of 62
Describe the process of genetic drift
Individuals show genotypic variation, by chance one allele is passed on more often than the others, number of individuals with that allele increases,
28 of 62
When does genetic drift normally have a greater effect?
On smaller populations where chance has greater influence - this may have been caused by a natural disaster leading to a genetic bottleneck
29 of 62
Name an example of where genetic drift has occured
When different Native American tribes show different blood group frequencies (blood group doesn't affect survival btw) - by chance, blood group O was passed on more often in the Navajo tribe, where as Blackfoot Indians are mainly blood group A
30 of 62
What does the Hardy-Weinberg Principle do?
Predicts allele and genotype frequency within populations
31 of 62
What are the conditions needed for the Hardy-Weinberg Priniciple to be valid?
Large population, no immigration, emigration, mutations or natural selection, must be random mating
32 of 62
What is the p used for in the HW Principle?
Frequency of the dominant allele
33 of 62
What is the q used for in the HW Principle?
Frequency of the recessive allele
34 of 62
What is the first formula for the HW Principle?
p + q = 1
35 of 62
Why does p + q = 1?
Because the total frequency of all possible alleles for a characteristic in a certain population is 1, so the frequencies of all the dominant and recessive alleles must add up to 1
36 of 62
What is the second formula for the HW Principle?
p^2 + 2pq + q^2 = 1
37 of 62
What is p^2?
Frequency of the homozygous dominant genotype (AA)
38 of 62
What is 2pq?
Frequency of the heterozygous genotype (Aa)
39 of 62
What is q^2?
Frequency of the homozygous recessive genotype (aa)
40 of 62
Give an example of a use of the HW Principle
Estimating the proportion of people in the UK that are cystic fibrosis carriers (Ff) when you know that 1/2000 people born have cystic fibrosis (ff) - ie. you need to find 2pq
41 of 62
Define artificial selection
When humans select individuals in a population to breed together to get desirable traits
42 of 62
What are the 2 examples you need to learn for artificial selection?
Modern dairy cow and bread wheat
43 of 62
Describe the process of artificial selection in the modern dairy cow
Select female with high milk yeild and male whose mother had a very high milk yield, breed these 2 together, select offspring with highest milk yields, breed them together, continue this over several generations
44 of 62
Describe the process of artificial selection in bread wheat
Breed together wheat plants with a high wheat yield (e.g. large ears), breed offspring with the highest wheat yields, continue over several generations
45 of 62
What is artificial selection also know as?
Selective breeding
46 of 62
What are the similarities between natural and artificial selection?
Both selections change the allele frequency in the next generation - more desirable characteristics become more common / Both make use of random mutations when they occur - if it produces a beneficial/desirable characteristic
47 of 62
What are the differences between natural and artificial selection?
Selected by the environment or humans / The result of natural selection is unpredictable but artificial selection aims for a predetermined result / Natural s. makes species better adapted to environment, artificial s. makes species useful for humans
48 of 62
Define a species
A group of similar organisms that can reproduce to give fertile offspring
49 of 62
Define speciation
The development of a new species
50 of 62
When does speciation occur?
When populations of the same species become reproductively isolated and then changes in allele frequency cause changes in the phenotype that means they can no longer breed together to produce fertile offspring
51 of 62
What are the 2 ways that speciation occurs?
Geographical isolation or reproductive isolation
52 of 62
Describe the process of geographical isolation
Physical barrier separates a population of a species, conditions either side will be different, different selection pressures, natural selection, different characteristics will be advantageous on each side, change so much can't interbreed any more
53 of 62
Name some things that cause geographical isolation
Floods, volcanic eruptions, earthquakes, mountain range, river
54 of 62
What are the changes that lead to reproductive isolation?
Seasonal changes - different mating seasons / Mechanical changes - incompatible sex organs / Behavioural changes - perhaps a courtship dance is not recognised
55 of 62
What is the biological species concept?
A species is a group of similar organisms that can reproduce to give fertile offspring
56 of 62
Why do scientists have problems with the biological species concept?
Deciding which species an organism belongs too or if it's sufficiently different to be classed as a new species / can't always see their reproductive behavious - extinct, asexually reproduce, practical/ethical issues as you can't see them in the wild
57 of 62
What is the phylogenetic species concept?
The study of the evolutionary history of groups of organisms - tells us what's related to what, and how closely related they are
58 of 62
What is the phylogenetic species concept also known as?
The cladistic or evolutionary concept
59 of 62
How does the phylogenetic species concept work?
All organisms have evolved from shared common ancestors so the more closely related 2 species are, the more recently their last common ancestor will be
60 of 62
Name a problem associated with the phylogenetic species concept
There's no cut-off point to say how different 2 organsisms have to be to be different species - e.g. chimps and humans are different species but we share about 94% of our DNA with them
61 of 62
How is a species classified using the phylogenetic species concept?
If an organism is closely related to members of another species, it's probably the same species/ if it's quite different to any known species, it's probably a new species
62 of 62

Other cards in this set

Card 2

Front

Describe the characterstics of continuous variation

Back

No distinct categories, often influenced by many genes (polygenic)

Card 3

Front

Give 2 examples of continuous variation

Back

Preview of the front of card 3

Card 4

Front

Give 2 examples of discontinuous variation

Back

Preview of the front of card 4

Card 5

Front

Describe the characterstics of discontinuous variation

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all DNA, genetics and evolution resources »