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AQA A LEVEL Biology > Section 7 Population, Evolution, Inheritance > Flashcards

Section 7 Population, Evolution, Inheritance Flashcards

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1
Q

What is a species?

A

A group of organisms that can breed together to produce a fertile offspring

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2
Q

What is a population?

A

The amount of a certain species within a particular place

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3
Q

What is a community?

A

The entire population of the different species in a particular place

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4
Q

What is a habitat?

A

The place where a organism lives

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5
Q

What is an ecosystem?

A

A mix of different communities and habitats and how they interact via abiotic and biotic factors

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6
Q

What is an ecological niche?

A

An organisms role/ position within an ecosystem in terms of its interaction with abiotic and biotic factors.

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7
Q

Why can 2 different species not occupy the same niche?

A

Due to intraspecific competition based on biotic and abiotic factors one species will out compete the other into extinction. This is known as the competitive exclusion principle.

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8
Q

How to sample plant species over a large area?

A

Obtain a map of the area

Divide the map into grids

Select a large number of coordinates using a running mean

Select a random set of coordinates using a random number chart

in each coordinate place a quadrat

Measure the abundance of plant species in whatever way (percentage or individual)

calculate the average number of the whole area.

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9
Q

How to sample plant species along a path?

A

Using a transect

Place a tape along the path count the number of plants (line transect)

OR

Place a tape along the path and at regular intervals place a quadrat and calculate the average abudance for the total amount of quadrats. (Belt transect)

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10
Q

How to sample animal species in an area?

A

Mark release recapture technique

Set a trap

Capture the animal species

Mark them (tag or florescent marker-ensuring it is not toxic and not harmful

Release them

After some time begin trap again

Count the number of marked and non marked in the second collection

Calculate the total estimated population

(Total number of sample 1 x total number of sample 2)/ marked in sample 2

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11
Q

What assumptions are made when using the mark-release-recapture method?

A

When using the mark-release-recapture method you are assuming that:

There was no immigration or emigration during the population mixing time

no births of death

marked animals distribute evenly back into the population

mark is non toxic

mark does not come off

large population

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12
Q

What are the 3 stages of population?

A

Slow/lag phase: Species becomes adapted to new environment

Rapid/log phase: species adapted abundant resources. doubling the rate of reproduction (Birth rate > Death rate)

Stationary phase: resources become limited, instraspecific competition occurs birth rate= death rate

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13
Q

How are resources and limiting factors grouped?

A

Abiotic (non-living): light, temperature, temperature, water, oxygen and carbon dioxide, pH and living space

Biotic (living): Predator, prey, mates, competition, disease

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14
Q

What is competition?

A

when organisms compete for resources abiotic and biotic.

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15
Q

What are the 2 types of competition?

A

InTRAspecific: Occurs between organisms within the SAME SPECIES only occurring when resources become limited= natural selection and adaptation.

InTERspecific: Occurs between organisms within DIFFERENT SPECIES and can occur at any time and leads to the formation of climax communities.

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16
Q

Describe the predator prey relationship?

A

Prey increases in number

More food available for predator

Predator increases in number

Predator eats more prey

Prey decreases in number

Less food availability for predator

Predator number decreases

Less prey are eaten

Prey increases in number (CYCLE REPEATS)

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17
Q

What is succession?

A

How an ecosystem changes overtime

(change in species diversity and habitat diversity) relies on environment being made less hostile by present species via death and decomposition leading to it being outcompeted and replaced by larger, better adapted species.

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18
Q

What are the 2 types of succession?

A

Primary (occurs in new land)

Secondary (occurs on previously colonised land that has become bare e.g. after a forest fire)

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19
Q

Describe primary succession (PROCESS)

A

New land appears

Pioneer species settle (adapted to surviving in hostile condition

Pioneers are: producers and have mutualistic NFB

asexually reproduce (one parent, genetically identical, faster)

Xerophytes

Can handle extreme conditions

Have wind dispersed seeds which can anchor to land

Overtime the land erodes and forms, Pioneer species die and decompose adding nutrients to the soil

Plants can now grow which outcompete the Pioneer species

Overtime, more soil forms, small plants die out adding more nutrients to the soil.

Larger plants can now grow outcompeting the smaller plants

This process continues until the climax community is reached

The climax community has the best adapted species to their environment.

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20
Q

What are the properties of succession?

A

Species diversity increases

Habitat diversity increases

Environment becomes less hostile

Food chains become more complex and biomass increases

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21
Q

Primary vs secondary succession

A

Secondary starts from small plants Pioneer species and secondary succession is faster.

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22
Q

How can conservation be used to prevent succession?

A

Used to prevent formation of woody forests

Involves deforestation, burning trees and using pesticides

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23
Q

What is evolution?

A

A change in allele frequency within a population

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24
Q

What are the 2 types of evolution?

A

Adaptation and speciation

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25
Q

What is adaptation?

A

A species adapting to changes in the environment driven by natural selection where most of the individuals in the species will have the favourable allele to be adapted to their environment.

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26
Q

What is the process of adaptation?

A

The variation in population of species

New alleles by random mutation

Environment applies a selection pressure on the population

Those with favourable characteristics alleles survive, the other die

The ones that survive will reproduce passing on their favourable genes =reproductive success

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27
Q

What are the 3 types of selection?

A

Stabilising, directional and disruptive

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28
Q

What is stabilising selection?

A

When the environment favours those with the most common characteristics and the extremes die out.

The common characteristic increases in proportion

The range (standard deviation) will reduce

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29
Q

What is directional selection?

A

When the environment favours those individuals with characteristics on one of the extremes

Overtime this will become the most common characteristic

Normal distribution will shift to that extreme

30
Q

What is disruptive selection?

A

When the environment changes between both extreme conditions

Hence individuals on both extremes are favoured at different times and increase in number

Those in the middle (average) will decrease in number

31
Q

What is speciation?

A

Process by which new species arise from existing species

32
Q

What are the 2 types of speciation?

A

Allopatric and sympatric

33
Q

What is allopatic speciation?

A

Speciation that is driven by geographical isolation

34
Q

Describe Allopatic speciation

A

Start with a population of species

Variation in the population

Population separated into different groups by geographical isolation

Each group is exposed to different environments/ selection pressures

Each group undergoes different directional selections

Therefore each group changes so much in genetic diversity that they can no longer interbreed with each other to produce fertile offspring

Changes include different courtship behaviour or incompatible gametes

35
Q

What is sympatric speciation?

A

Speciation occurring in the same geographical area

36
Q

What is inheritance?

A

Offering inheriting a combination of alleles for each gene that will help determine the characteristics

37
Q

What is a gene?

A

A section of DNA that codes for a protein

38
Q

What is an allele?

A

A form of a certain gene

39
Q

What is a dominant allele?

A

An allele that is always expressed if present

40
Q

What is a recessive allele?

A

An allele that is only expressed if 2 of these alleles are present.

41
Q

What is a genotype?

A

Combination of all alleles for a particular gene

42
Q

What is a phenotype?

A

Expressed or observed characteristic

43
Q

What is homozygous?

A

When 2 allele are both either dominant or both recessive

44
Q

What is heterozygous?

A

having 2 different alleles

45
Q

What is monohybrid inheritance?

A

Inheritance dealing with one characteristic

e.g. Dominant, recessive, co dominant, multiple allele, sex linkage

46
Q

What is the expected ratio for monohybrid dominant/ recessive?

A

3 dominant 1 recessive.

47
Q

Why are observed ratios different that expected?

A

random fertilisation of gametes

Small size

Mutation

Selection

48
Q

How can 2 parents with a dominant characteristic give birth to child with a recessive characteristic?

A

If both parents are heterozygous they have a 25% chance of giving birth to a child who is homozygous recessive

49
Q

What is co-dominance?

A

When 2 different dominant alleles are inherited, both will be expressed in the phenotype

50
Q

What are multiple alleles?

A

When the gene has more than 2 alleles

51
Q

Alleles for blood group?

A 
Ia, Ib, Io
Ia gives A antigen on RBC
Ib gives b antigen on RBC 
Io gives no antigen on RBC
Ia, Ib are codominant 
Io is recessive
52
Q

Genotypes/phenotypes for blood group?

A 
A= IaIa, IaIo 
B= IbIb, IbIo 
AB= Ia Ib
o= IoIo
53
Q

Can recieve blood from whom?

A 
A= from A&O
B= from B&O
AB= from A,B,AB,O 
O= only from O
54
Q

What is a sex linked gene?

A

A gene carried on one of the sex chromosomes, normally the X chromosome

55
Q

What is an inherited disease?

A

Inheriting a mutated allele that leads to production of a faulty protein, normally a recessive allele

56
Q

What is a sex linked disease?

A

Inheriting a mutated allele carried on one of the sex chromosomes, normally, a recessive allele & normally carried on X chromasone.

57
Q

Why do males have increased chance of inheriting a sex linked disease rather than females?

A

Males only have 1 X chromosome, females have 2 X chromosomes, females can be carriers, males cannot be carriers

58
Q

What is dihybrid inheritance?

A

Inheritance dealing with 2 characteristics rather than one

E.g.
Dominant recessive
Autosomal linkage
Epistasis

59
Q

What is the expected ratio for dihybrid dominant/recessive?

A

9 Dominant/Dominant
3 Dominant/Recessive
3 Dominant/Recessive
1 Recessive/Recessive

60
Q

What is autosomal linkage?

A

2 genes (characteristics) carried on the same chromosome

61
Q

What is epistasis?

A

The interaction between different genes

62
Q

What are the 3 types of epistasis?

A

Dominant

Recessive

Complementary

63
Q

What is dominant epistasis?

A

Dominant genotype on one gene which inhibits the expression of another gene

64
Q

What is the expected ratios of epistasis?

A 
12 Epistasis (Inhibited)
3 Expressed (Dominant)
1 Expressed (Recessive)
65
Q

What is recessive epistasis?

A

The recessive genotype on one gene which inhibits the expression of other genes.

66
Q

What is the expected ratio for recessive epistasis?

A 
9 Expressed (Dominant)
3 Expressed (Recessive)
4 Epistasis (Inhibited)
67
Q

What is complementary epistasis?

A

A dominant genotype required on both genes to achieve final product.

68
Q

What ratio is expected for complementary epistasis?

A

9 Final product

7 None

69
Q

What does the hardy weinburg principle calculate?

A

Frequency of an allele in a population

70
Q

What does the HWP assume?

A

That the frequency will not change over time based on:

An isolated population
A large population
Random mating
No mutation
No selection
71
Q

What is the Hardy weinburg principle?

A 
p= frequency of dominant allele
q= frequency of recessive allele 
p+q= 1 (100 percent of the total population)
P^2= frequency of homozygous dominant
2pq= frequency of heterozygous 
p^2+2pq= Frequency of the dominant condition

q^2= frequency of homozygous recessive

p^2+2pq+q^2=1

AQA A LEVEL Biology (8 decks)

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