ecology topic 7 Flashcards
(97 cards)
1
Q
what is a gene?
A
a sequence of bases on DNA that code for a protein, which results in a characteristic
2
Q
what is an allele?
A
different versions of a gene
3
Q
what is a genotype?
A
genetic makeup of an organism/the alleles that an organism has
4
Q
what is a phenotype?
A
the genetic makeup of an organism and its interactions with the environment to produce the organism’s characteristics
5
Q
what does dominant mean?
A
allele whose characteristic appears in the phenotype even when there is only one copy
6
Q
what does recessive mean?
A
allele whose characteristic appears in the phenotype if two copies are present
7
Q
what does co dominant mean?
A
alleles are both expressed in the phenotype- neither are recessive
8
Q
what does locus mean?
A
the fixed position of a gene on a chromosome
9
Q
what does homozygote mean?
A
an organism that carries two copies of the same allele
10
Q
what does heterozygote mean?
A
organim carries two different alleles
11
Q
what does a carrier mean?
A
person carrying an allele which is not expressed in the phenotype, but can be passed onto offspring
12
Q
what does a diploid organism have?
A
two sets of chromosomes
13
Q
how many alleles do diploid organisms have for each gene?
A
2
14
Q
what is monohybrid inheritance?
A
inheritance of a characteristic controlled by a single gene
15
Q
what is dihybrid inheritance?
A
inheritance of two different characteristics simultaneously
16
Q
where is the genetic information for biological sex carried?
A
on two sex chromosomes
17
Q
what chromosomes do females have?
A
XX
18
Q
what chromosomes do males have?
A
XY
19
Q
when is a characteristic sex linked?
A
when the allele that it codes for is located on a sex chromosome
20
Q
which is the smaller chromosome, therefore carrying less genes?
A
y chromosome
21
Q
why are males more likely to show recessive phenotypes for sex linked genes?
A
males only have one X chromosome so express the characteristic even if it is recessive
22
Q
what is an autosome?
A
chromosome that isn’t a sex chromosome
23
Q
what is variation?
A
the differences that exist between individuals
24
Q
what is the name for variation within a species?
A
intraspecific variation
25
what does variation within a species mean?
individuals within a species can show a range of phenotypes
26
how can genetic variation occur within a species?
organisms have different alleles
27
what does genetic variation arise due to?
mutations, meiosis (during crossing over/independent segregation), random fertilisation and the environment
28
what are selection pressures?
enviornmental factors that limit the population of a species
29
what is the gene pool?
total number of alleles of all the genes of all the individuals of a population during a given time
30
how does natural selection occur?
1) individuals of the same species vary due to differences in alleles
2) predation, disease and competition create a pressure for survival
3) as individuals vary, some are better adapted to selection pressures than others
4) individual with a phenotype that increases their chance of survival are more likely to survive/reproduce/pass on genes
5) greater proportion of a population inherit beneficial alleles
6) more likely to survive/reproduce and pass on genes
7) frequency of beneficial alleles increases across generations
31
what is overproduction?
where each generation has more offspring than can be supported by the environment
32
how does overproduction link to natural selection?
competition occurs for limited resources
33
what is stablising selection?
where individuals with alleles for characteristics towards the middle of the range are most likely to survive and reproduce
34
when does stablising selection occur?
when the environment isn't changing
35
what is the result of stablising selection?
reduced range of possible phenotypes
36
what is directional selection?
where individuals with alleles for a single extreme phenotype are more likely to survive and reproduce
37
when does directional selection occur?
in response to an environmental change
38
what is disruptive selection?
where individuals with alleles for extreme phenotypes are more likely to survive and reproduce
39
when does disruptive selection occur?
when the environment favours more than one phenotype
40
what is speciation?
the development of a new species from an existing species
41
when does speciation occur?
when populations of the same species become reproductively isolated
42
what happens when animals become reproductively isolated?
changes in allele frequency cause a change in phenotype, so they can no longer interbreed to produce fertile offspring
43
why does allopatric speciation occur?
due to geographical isolation
44
why does geographical isolation lead to allopatric speciation?
experience different conidtions on different sides of the geographical barrier
45
what are the stages of allopatric speciation?
physical barriers stop interbreeding between populations
populations adapt to new environments
allele and phenotype frequencies change which leads to the development of new species
46
why does sympatric selection occur?
populations become reproductively isolated due to differences in their behaviour
47
why could sympatric selection result?
due to random mutations which prevent breeding
48
what is a habitat?
place where an organism lives
49
what is a population?
all the organisms of one species in a habitat
50
what is a community?
populations of different species
51
what is an ecosystem?
a comminity made up of biotic and abiotic factors
52
what are abiotic factors?
non living features of an ecosystem
53
what are biotic factors?
living features of an ecosystem
54
what are examples of abiotic conditions?
temperature, water availability
55
what are examples of biotic conditions?
living features of an ecosystem
56
what is a niche?
role of the species within its habitat
57
what is an adaptation?
feature of a species that increases its chance of survival and reproduction
58
what does a niche include?
a species biotic and abiotic interactions
59
how many species can a niche be occupied by?
1
60
what happens if two species try to occupy the same niche?
have to compete with each other
61
what are the types of adaptations?
physiologial, behavioural, anatomical
62
what are physiological adaptations?
processes within the body
63
what are behavioural adaptations?
how an organism acts
64
what are anatomical adaptations?
structural features of an organism
65
what is population size?
the total number of organisms of one species in a habitat
66
what is carrying capacity?
the maximum stable population size that an ecosystem can support
67
why does carrying capacity vary?
due to biotic and abiotic factors
68
what are the three biotic factors that cause variation in population size?
interspecific competition
intraspecific competition
predation
69
what is interspecific competition?
competition between different species
70
what is intraspecific competition?
competition within a species
71
what is predation?
where an organism kills and eats another organism (prey)
72
how does temperature affect population size?
further away from optimum temp=less likely to survive
73
how does light affect population size?
increase in light=increased rate of photosynthesis= larger carrying capacity
74
how does pH affect population size?
optimum pH= largest population size
75
how does water affect population size?
where water is scarce= smaller population size, only those adapted survive
76
how does humidity affect population size?
affects transpiration rate in plants and evaporation of water in animals/humans, those best adapted survive
77
how do you select a random sample?
choose an area to sample, divide site into a grid and use a random number generator to select co ordinates, use an appropriate technique to select a sample, repeat the process
78
what is a non motile organism?
organism that doesn't move about
79
what is a quadrat?
a square frame, divided into a grid of smaller squares, placed on the ground in the area you are investigating
80
what is species frequency?
how often a species is found
81
what is percentage cover?
amount of quadrat covered by the species (count a square if it is over halfway covered)
82
what is a transect used for?
investigating how plants are distributed across an area
83
what happens in a belt transect?
quadrats are placed next to each other along the transect to work out species frequency and percentage cover along the transect
84
what happens in an interrupted belt transect?
quadrats are placed at intervals along a transect
85
what is mark release recapture used to investigate?
the abundance of motile species
86
how do you perform mark release recapture?
1) capture a species using an appropriate technique and count
2) mark in a harmless way
3) release back into their habitat
4) wait a week and take a second sample from the same population
5) count how many of the second sample are marked
87
what is the equation for total population size?
number caught in 1st sample x number caught in 2nd sample
/number marked in second sample
88
what assumptions are used in mark release recapture?
marked sample has had enough time to mix back in with the population
marking hasn't affected an individual's chance of survival
marking itself is still visible
no changes in population size during the period of the study
89
what is succession?
the process in which an ecosystem changes over time (changes to biotic and abiotic conditions)
90
what is primary succession?
happens on land that has been newly formed/exposed, no soil or organic matter to start with
91
what is secondary succession?
happens of land cleared of plants, but soil remains
92
what is the first species to colonise an area called?
the pioneer species
93
what are the stages of primary succession?
1) abiotic conditions are harsh so only pioneer species can grow
2) pioneer species changes the abiotic conditions, and as they die a basic soil is formed
3) this makes the conditions less hostile, which means that organisms with different adaptations can grow
4) these die/are decomposed so the soil is deeper and richer in minerals
5) larger plants can grow so the soil can maintain more water
6) new species compete and change the environment
94
what are the stages for secondary succession?
same as primary succession but starts at a later stage as there is already a soil layer
95
what is the final stage of succession called?
the climax community
96
what are the features of a temperate climate?
plenty of water
mild temperatures
little change between seasons
large trees due to deep soils
97
what are the features of a polar climate?
little available water
low temperatures
drastic changes between the seasons
only herbs/shrubs- no large trees
