Population Ecology Flashcards

1
Q

What is ecology?

A
  • the study of the interactions of organisms with their physical and biological environments
  • and how these determine the distribution and make-up of populations within an ecosystem
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2
Q

What is population ecology?

A
  • population ecology is concerned with fluctuations in the size of a population and the factors, both physical and social that regulates these fluctuations
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3
Q

What is the biosphere?

A
  • the part of the earth where living organisms are found
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4
Q

What is an ecosystem?

A
  • made up of groups of different species of organisms that interact with each other and with the environment
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5
Q

What is an organism?

A
  • an individual form of life, composed of a single cell or a complex of cells that are capable of growing and reproducing
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6
Q

What is a community?

A
  • a group of different species that inhabit and interact in a particular area
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7
Q

What is a species?

A
  • a group of closely related organisms that are very similar to each other and are usually capable of interbreeding and producing fertile offspring
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8
Q

What is an individual?

A
  • a single organism capable of independent existence
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9
Q

What is a population?

A
  • a group of organisms of the same species that occupy the same area and can breed freely with each other
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10
Q

What is population size?

A
  • the total number of individuals in a population
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11
Q

What factors affect the size of a population?

A
  • natality
  • mortality
  • immigration
  • emigration
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12
Q

What is natality?

A
  • the birth rate in animals or the production of seeds in plants
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13
Q

What is mortality?

A
  • the death rate
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14
Q

What is immigration?

A
  • individuals move into a population and stay
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15
Q

What is emigration?

A
  • individuals leave a population and do not return
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16
Q

What is the birth rate in humans?

A
  • the number of births per 1000 people in a year
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17
Q

What is the death rate in humans?

A
  • the number of deaths per 1000 people in a year
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18
Q

When do populations grow?

A
  • when birth and immigration exceed death and emigration
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19
Q

When do populations decline?

A
  • when death and emigration exceed birth and immigration
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20
Q

When do populations remain stable?

A
  • when birth and immigration approximately equal death and emigration
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21
Q

When does the number of individuals increase exponentially?

A
  • if a few individuals enter an unoccupied area where there is no shortage of food or other resources and no predators, they will reproduce
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22
Q

What does exponential mean?

A
  • increasing more and more rapidly
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23
Q

What builds up environmental resistance?

A
  • as the numbers increase, more demands are made on the available resources and this builds up environmental resistance
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24
Q

What does environmental resistance cause?

A
  • the birth rate/immigration rate to decrease
  • and the death rate/emigration rate to increase
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25
Q

What happens when a balance is reached?

A
  • the population stabilises at a particular size or number
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26
Q

What is the carrying capacity?

A
  • the population density that the environment can support
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27
Q

What does the population fluctuate around?

A
  • around the carrying capacity until the environment changes again
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28
Q

When does population size fluctuate?

A
  • seasonally and annually
  • depending on the resources available
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29
Q

What kind of regulation does population size possess?

A
  • population size in an ecosystem is self-regulating
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30
Q

What are limiting factors?

A
  • the factors that help to regulate the growth of a population
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31
Q

What kinds of limiting factors are there?

A
  • density independent factors
  • density dependent factors
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32
Q

What are density independent limiting factors?

A
  • factors that limit the growth of a population as a result of natural factors and not because of the density or number of the organisms
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33
Q

What are the types of density independent factors?

A
  • physical factors
  • catastrophic events
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34
Q

What are some examples of density independent physical factors?

A
  • rainfall
  • temperature
  • humidity
  • acidity
  • salinity
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35
Q

What are some examples of density independent catastrophic events?

A
  • floods
  • fire
  • drought
  • volcanic eruptions
  • tsunami
  • earthquakes
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36
Q

What are density dependent limiting factors?

A
  • factors that have a greater effect when the population density is high
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37
Q

What happens when organisms are more crowded (density dependent factors)?

A
  • compete more for resources
  • are more easily found by predators
  • spread disease and parasites more readily
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38
Q

What are some examples of resources that organisms compete for when they are more crowded?

A
  • food
  • light
  • oxygen
  • water
  • space
  • shelter
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39
Q

What is a stable population?

A
  • one in which numbers decrease when its size exceeds the carrying capacity
  • but increase again when numbers fall below the carrying capacity
  • i.e. one that fluctuates around the carrying capacity
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40
Q

When does an unstable population develop?

A
  • if the population far exceeds the carrying capacity
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41
Q

What happens to the habitat of an unstable population?

A
  • deteriorates rapidly, leading to a lowering of the carrying capacity
  • eventually not able to support the population, which will decrease rapidly and possibly become extinct
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42
Q

What do direct methods involve?

A
  • counting every single individual in a population - this is called a census
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43
Q

What are the types of methods used to estimate population size?

A
  • direct methods
  • indirect methods
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44
Q

When can direct methods be used?

A
  • for populations where organisms are large enough to be seen
  • where the area in which the animals are being counted is not too large
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45
Q

For what kind of individuals can direct methods be used?

A
  • slow moving (e.g.
  • stationary (e.g. plants)
  • usually stay in a fixed position (e.g. barnacles)
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46
Q

What can be used if the area is too large to count every individual at one time?

A
  • aerial photographs can be used to show the whole area in which the population occurs
  • helicopters can be used to count larger animals
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47
Q

What do indirect methods involve?

A
  • counting a sample number of the population and then using simple calculations to estimate the total size of the population
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48
Q

What are some examples of indirect methods?

A
  • quadrat method
  • mark-recapture method
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49
Q

What does the quadrat method involve?

A
  • involves counting the number of individuals in small measured areas (quadrats)
  • and then using these numbers to calculate the population size of the total area with the aid of the quadrant formula
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50
Q

What is the formula for the total population when using the quadrant method?

A

[numbers in sample x size of whole habitat] ÷ size quadrat

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51
Q

What is the purpose of using a quadrat?

A
  • to enable comparable samples to be obtained from areas of consistent size and shape
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52
Q

What is important to do when using quadrats?

A
  • quadrats should be distributed at random
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53
Q

Why is random sampling important?

A
  • as the distribution of individuals may not be uniform throughout the area
  • it is important to sample as many quadrats of the total area as possible
  • to achieve a true reflection of the distribution
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54
Q

What does the mark-recapture method involve?

A
  • a known number of individuals is caught and marked and then released
  • after a suitable time period another sample is captured and the number of marked individuals counted
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55
Q

What is the formula used in the mark-recapture method?

A

P = (M x C) ÷ R

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56
Q

What does the P symbolise in the mark-recapture method formula?

A

P = estimated population

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57
Q

What does the M symbolise in the mark-recapture method formula?

A

M = total number of marked animals

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58
Q

What does the C symbolise in the mark-recapture method formula?

A

C = total number of animals caught in the second sample

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59
Q

What does the R symbolise in the mark-recapture method formula?

A

R = total number of animals marked in the second sample (i.e. recaptured)

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60
Q

What precautions must be taken for a reliable result in terms of time?

A
  • only a short time should pass between the first and second sampling
  • so that no births and deaths can occur
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61
Q

What precautions must be taken for a reliable result in terms of repetition?

A
  • sampling should be repeated several times and an average population calculated
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62
Q

What precautions must be taken for a reliable result in terms of the actual marking?

A
  • the marking must not damage the individual or affect its movement or behaviour
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63
Q

What precautions must be taken for a reliable result in terms of the marked animal?

A
  • the marked animal must mix freely with the rest of the population before a new sample is taken
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64
Q

What precautions must be taken for a reliable result in terms of immigration and emigration?

A
  • no immigration or emigration is allowed
  • i.e. the population must be closed
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65
Q

What is the significance of all living organisms within an ecosystem being interdependent?

A
  • this means that changes in the population size of one species can drastically affect that of another
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66
Q

What is predation?

A
  • a biological interaction where one species kills and eats another species
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67
Q

What does the role that predators play in their environment do?

A
  • helps to create and maintain greater diversity within an ecosystem
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68
Q

How do predators create and maintain greater diversity within an ecosystem in terms of regulation?

A
  • by regulating the abundance and distribution of prey species
  • as the predator population increases, the prey population decreases
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69
Q

How do predator and prey evolve in relation to one another?

A
  • they evolve together and are part of the same environment
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70
Q

How do predators create and maintain greater biodiversity within an ecosystem?

A
  • by increasing the biodiversity of communities by preventing a single species from becoming dominant
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71
Q

How do predators create and maintain greater diversity within an ecosystem in terms of genetics?

A
  • by keeping the prey population genetically fit by removing sick, injured and weak individuals
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72
Q

How do predators create and maintain greater diversity within an ecosystem in terms of food?

A
  • by providing vital food sources for scavengers
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73
Q

What does the feeding relationship between the predator and the prey determine?

A
  • determines the size of the two populations by means of a negative feedback mechanism
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74
Q

What happens to the predator population as the prey population decreases due to predator killing?

A
  • the food available for the predators is less
  • and so their numbers subsequently decline
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75
Q

What happens to the prey when predator pressure is reduced?

A
  • the numbers of the prey can increase once again
  • and the cycle goes on
76
Q

What is competition?

A
  • when two or more individuals compete for the same resources that are in short supply
77
Q

What resources to individuals compete over?

A
  • light
  • space
  • water
  • food
  • shelter
78
Q

What are the types of competition?

A
  • intraspecific competition
  • interspecific competition
79
Q

Between whom does intraspecific competition occur?

A
  • between individuals of the same species
80
Q

What does intraspecific competition include?

A
  • competition for mates as well as basic resources
81
Q

Why is intraspecific competition more intense than interspecific competition?

A
  • because members of the same species have similar habitats and resource requirements
82
Q

Between whom does interspecific competition occur?

A
  • between individuals of different species where the niches in a habitat are very similar
83
Q

What is an ecological niche?

A
  • all the conditions necessary for an organism to survive and reproduce
84
Q

What is needed in order for a population to survive?

A
  • its individuals must survive and reproduce
85
Q

What must individuals do in a population to ensure survival and reproduction?

A
  • tolerate the physical environment (temperature, pH)
  • obtain energy and nutrients
  • cope with competition
  • avoid predators
86
Q

What happens when two species with the same or similar ecological niches occupy the same habitat?

A
  • their ecological niches will overlap to a greater or lesser extent
87
Q

What is specialisation?

A
  • the structural and behavioural adaptations that enable individuals of different species to co-exist
88
Q

What does the competition that arises from overlapping ecological niches result in?

A
  • competitive exclusion
  • competitive coexistence
89
Q

When does competitive exclusion occur?

A
  • when one of the two competing species is much more successful than the other
90
Q

When does competitive coexistence arise?

A
  • it arises when two competing species coexist in the same habitat
91
Q

What is resource partitioning?

A
  • the evolutionary process whereby species with similar requirements, living in the same habitat
  • evolve specialised traits that enable them to utilise the resources differently
  • creating separate niches to reduce interspecific competition and make coexistence possible
92
Q

What does resource partitioning contribute to?

A
  • the great diversity of species on earth
93
Q

How can resources be partitioned?

A
  • at different times
  • in different parts of a habitat
  • in different parts of the same plant
94
Q

What is stratification?

A
  • the pattern of many different trees and other plants of varying size and species creating a vertical structure that divides the vegetation into layers
95
Q

How does light intensity differ in vegetation?

A
  • the intensity of light diminishes as the rays pass through the different layers of forest vegetation
96
Q

How is light partitioned in plants?

A
  • the different layers of vegetation are adapted to photosynthesis in different light intensities
97
Q

How are resources partitioned by giraffes and kudu in woodland savannah areas?

A
  • kudu browse on the lower branches and giraffe on the upper branches
98
Q

What is ecological succession?

A
  • a predictable pattern of gradual change over time in the types of species in a community following a disturbance
99
Q

What are the types of ecological succession?

A
  • primary succession
  • secondary succession
100
Q

Where does primary succession begin?

A
  • on sites that have not previously had plants growing on them
  • e.g. beaches, ponds, bare rock
101
Q

Where does secondary succession begin?

A
  • in areas where a disturbance removes some or all species but the soil remains
102
Q

What are the characteristics of community structure?

A
  • not static
  • determined over time by succession that takes place as a result of certain factors
103
Q

What determines community structure?

A
  • disturbances
  • competitive interactions
104
Q

What are the kind of disturbances that influence community structure caused by?

A
  • physical disasters (e.g. storms, floods, fires)
  • humans or animals (e.g. abandoned crop field, overgrazed area, logged forest)
  • climate change
105
Q

How do disturbances determine community structure?

A
  • creates opportunities for new species to move in
  • new species alter the character of the community
  • creating an environment suitable to even newer species
106
Q

What are the competitive interactions that influence community structure?

A
  • competition
  • predation
107
Q

What are the stages of ecological succession?

A
  1. Pioneer species stage
  2. Intermediate species stage
  3. Climax community
108
Q

Where do pioneer species grow best?

A
  • bare ground conditions
  • where there is little competition for space and resources
109
Q

What are the features of pioneer species?

A
  • hardy
  • establish rapidly
  • have spores or seeds that can disperse over long distances
  • do now grow in shade
110
Q

Why do pioneer species need to be hardy?

A
  • to withstand extreme variations in temperature and moisture
111
Q

What do pioneer species do?

A
  • prepare the surroundings for later colonists
  • by altering the biotic and abiotic environment
112
Q

How do pioneer species prepare the surroundings for later colonists?

A
  • build-up, stabilise and enrich the soil
  • alter the amount of light available by providing shade
113
Q

What is an example of a floral pioneer species involved in primary succession?

A
  • lichens
114
Q

How are lichens beneficial in primary succession?

A
  • don’t need soil
  • help to form soil as lichens and physical weathering break down rocks into smaller pieces
  • add small amounts of organic matter to newly formed soil when they die and decompose
115
Q

What plants follow lichens in the pioneer species stage?

A
  • mosses and other simple plants
116
Q

What are examples of faunal pioneer species?

A
  • mites
  • ants
  • spiders
  • small herbivores
  • other decomposers such as earthworms
117
Q

When does secondary succession in the pioneer species stage occur?

A
  • when the soil layer thickens
118
Q

What are the pioneer species of a secondary succession?

A
  • annuals (herbs and weeds) are the first to appear after a disturbance
  • grasses and perennials appear a year or so later
  • in forest gaps or wetter sites a tangle of climbers develops
119
Q

Why do ecological conditions change and lead to the intermediate species stage?

A
  • the soil can hold more water and is more fertile
  • temperatures are less extreme as there is more shade
120
Q

What happens in the intermediate species stage as the soil builds up?

A
  • small non-woody herbaceous species give way to small hardy woody plant species
  • these turn into larger woody shrubs and bushes that are much slower growing
  • grasses remain
121
Q

What animals become part of the community during the intermediate species stage?

A
  • larger herbivores (hares, small antelope)
  • small carnivores (caracal, wild cats)
  • snakes
  • raptors
122
Q

How do the intermediate species affect the communities?

A
  • they make the communities more structurally complex
123
Q

What is the climax community stage?

A
  • the last semi-stable stage
  • endpoint of succession
124
Q

How do climax communities vary?

A
  • large trees in a forest biome
  • or grasses and Acacia trees in a Savannah biome
  • dwarf, succulent shrubs in succulent karoo biome
125
Q

What are the characteristics of animal species in the climax community?

A
  • most diverse
  • include large herbivores and carnivores
126
Q

How is everything in a state of transition?

A
  • future disturbances can cause the species of a community to change
  • e.g. higher rainfall
127
Q

What environmental fluctuations determine an endpoint to a community?

A
  • rainfall
  • overgrazing
  • draining of wetlands
  • climate change
  • invasion by alien species
128
Q

How does rainfall determine successional endpoints?

A
  • amount of rain is the most important factor
  • e.g. if rainfall is more than 1200 mm/year the endpoint will be a forest community
  • e.g. prolonged drought means species able to withstand drier conditions will dominate and change the character of a forest community to a grassland or savannah endpoint
129
Q

How does overgrazing change a community?

A
  • grazers often choose one grass species, which changes the composition of the climax communities in the grassland biome
130
Q

How does the draining of wetlands affect successional endpoints?

A
  • permanently alters the environments
  • resulting in the disappearance of wetland climax species
131
Q

How does climate change affect successional endpoints?

A
  • climate change means some areas will get wetter and some will get drier
  • changing grasslands into forest communities and subsequently changing the climax communities
132
Q

How does invasion by alien species affect successional endpoints?

A
  • they replace the once dominant species in climax communities
133
Q

What is social organisation?

A
  • the structure of relationships within a group
134
Q

What features must be divided among a group to be socially organised?

A
  • resources
  • activities
135
Q

What resources must be divided among a group to be socially organised?

A
  • food
  • territories
  • nest sites
136
Q

What activities must be divided among a group to be socially organised?

A
  • protection
  • other skills like hunting
137
Q

Why is social organisation valuable?

A
  • it improves the survival and reproductive success of an individual
138
Q

What does social organisation make it easier to do?

A
  • avoid being attacked by predators
  • find food by hunting collectively
  • divide labour among individuals
  • find mates
  • protect resources
  • regulate population size
139
Q

What is the biggest advantage of forming a large group (flocking)?

A
  • the safety of the group is increased by avoiding and defending against predators
140
Q

Why are less prey captured when herds or flocks are formed in terms of awareness?

A
  • with many eyes and ears, the group as a whole is more watchful
  • particularly the individuals on the edge of the group
141
Q

Why are less prey captured when herds or flocks are formed in terms of mobbing?

A
  • a large herd or flock can mob a predator?
142
Q

What does it mean to mob?

A
  • to surround and overpower
143
Q

How does the dilution effect work?

A
  • the greater the number of individuals in a group, the greater the survival chances are of the individual
144
Q

How does the confusion and distraction effect work?

A
  • as a predator tries to single out its prey
  • the herd scatters in all directions
  • confusing the predator
145
Q

How do wild dog packs immobilise prey?

A
  • one dog grabs the prey’s tail and the other its upper lip
  • the rest of the pack then kills the prey quickly and efficiently
146
Q

How does the whole wild dog pack share in the kill?

A
  • the young feed first
147
Q

What happens to wild dogs left behind in the den?

A
  • they are fed on regurgitated meat
148
Q

What is the strict ranking system within African wild dogs?

A
  • it is led by the dominant alpha male and female who stay mates for life and prevent other females from bleeding
  • therefore they are the the only members of the pack that breed
149
Q

What happens to the offspring of African wild dogs?

A
  • the females reach sexual maturity at 18 months to 2 years, at which point they leave to join a new pack
  • the males remain with their pack for the rest of their lives
150
Q

What are the benefits of the type of social organisation practised by wild dogs?

A
  • the dominant pair keeps the pack under control which operates as a highly successful unit to ensure the survival of the species
  • raising the pups and caring for the old or sick is a group task
  • subordinate members of the group benefit in that they have access to mates and other shared resources
151
Q

What animals are the most advanced form of social organisation?

A
  • eusocial animals
152
Q

How do eusocial animals live?

A
  • in colonies
153
Q

What are the characteristics of the colonies in which eusocial animals live?

A
  • there is a dominant breeding pair or a single female (queen)
  • the non-breeding animals have different tasks to perform
154
Q

What kind of tasks do non-breeding eusocial animals do?

A
  • collect food
  • caring for the young
  • building, maintaining and protecting the nest
155
Q

Why could eusocial colonies not survive on their own?

A
  • environmental pressures such as shortage of resources
156
Q

What is eusociality?

A
  • a major evolutionary innovation
  • which has involved changes in life history, structure and behaviour
157
Q

What are some examples of eusocial animals?

A
  • termites
  • ants
  • some species of bee and wasp
  • the make mole-rat
158
Q

What is a colony?

A
  • a highly organised, integrated unit
159
Q

What does the termite caste system include?

A
  • reproductives
  • workers
  • soldiers
160
Q

What do the reproductives in the termite caste system include?

A
  • alates
  • queen and king
  • young reproductives
161
Q

What are alates and what do they do?

A
  • two, winged termites
  • appear in the rainy season and mate
  • each pair can found a new colony
162
Q

What do the queen and king in a termite colony do?

A
  • after losing their wings, they burrow underground
  • the eggs continuously laid by the queen hatch into nymphs which will grow into other castes with different roles
  • the king mates with the queen at regular intervals
163
Q

What do the young reproductives in a termite caste system do?

A
  • they will either become the new alates
  • or supplementary reproductive that can replace the queen and king should they die
164
Q

What do the workers in termite caste systems do?

A
  • can be male or female
  • make tunnels
  • build the termite mound
  • forage for food
  • look after eggs and nymphs
  • feed all members of the colony
165
Q

What do the soldiers in the termite caste system do?

A
  • develops huge biting or squirting mouthparts
  • that help with the defense of the colony
166
Q

How is the ratio of castes in a termite colony regulated?

A
  • the king and queen set a ratio of soldiers to workers and nymphs
167
Q

How have humans been able to reduce environmental resistance and increase the carrying capacity of the world’s food-producing regions?

A
  • food production has increased substantially
  • methods of treating diseases have improved greatly
168
Q

What has caused the exponential growth of the human population?

A
  • reduced environmental resistance
  • increased the carrying capacity of the world’s food-producing regions
169
Q

Why has food production increased substantially?

A
  • more land is being cultivated
  • improved methods of food production such as using artificial fertilisers to increase the yield of monoculture crops
170
Q

Which two groups can the countries of the world be divided into?

A
  1. more developed countries (MDCs)
  2. less developed countries (LDCs)
171
Q

What are the characteristics of more developed countries?

A
  • slow population growth
  • high standard of living
172
Q

What are the characteristics of less developed countries?

A
  • rapid population growth
  • lower standard of living
173
Q

What is a population pyramid?

A
  • a bar graph that shows the composition, by age and sex, of a nation’s population at the time of a census
174
Q

What are the main age/sex groups that a population contains?

A
  • pre-reproductive
  • reproductive
  • post-reproductive
175
Q

What is age structure?

A
  • the relative numbers of individuals of each age in a population
176
Q

What do the different population pyramid shapes depict?

A
  • a rapidly growing population
  • a stable population
  • declining population
177
Q

What are the characteristics of a rapidly growing population pyramid?

A
  • high birth rate
  • rapid fall in each upward age group due to high death rates
  • short life expectancy
  • commonly found in LDCs
178
Q

What are the characteristics of a stable population pyramid?

A
  • declining birth rate
  • low death rate
  • more people living due to old age
  • found in MCDs
179
Q

What are the characteristics of a declining population pyramid?

A
  • low birth rate
  • low death rate
  • higher dependency ratio
  • longer life expectancy as found in affluent countries
180
Q

What will happen to the population if the pre-reproductive age group is the largest?

A
  • the population will increase
181
Q

What will happen to the population if the pre-reproductive age group is the smallest?

A
  • the population will decrease
182
Q

What is the growth like in a population with more old, non-productive individuals?

A
  • it will grow more slowly
183
Q

What can population graphs do?

A
  • assess how rapidly or slowly a nation’s population is growing
  • show if a country is more or less developed
  • show the number of people per age range in the country
  • show the history of a nation’s growth
  • be useful in determining the number of economic dependents being supported
184
Q

How can epidemics cause the make-up of a population to change?

A
  • HIV/AIDS causing the deaths of many sexually active young men and women particularly in developing countries
185
Q

How can immigrants cause the make-up of a population to change?

A
  • high proportions of young immigrants being rapidly absorbed
  • or losses due to emigration of able-bodied young adults
186
Q

How can war cause the make-up of a population to change?

A
  • losses due to able bodied men fighting wars
187
Q

How can economic crisis cause the make-up of a population to change?

A
  • reduced birthrates during times of economic crisis