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
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
3
Q
What is the biosphere?
A
- the part of the earth where living organisms are found
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
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
6
Q
What is a community?
A
- a group of different species that inhabit and interact in a particular area
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
8
Q
What is an individual?
A
- a single organism capable of independent existence
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
10
Q
What is population size?
A
- the total number of individuals in a population
11
Q
What factors affect the size of a population?
A
- natality
- mortality
- immigration
- emigration
12
Q
What is natality?
A
- the birth rate in animals or the production of seeds in plants
13
Q
What is mortality?
A
- the death rate
14
Q
What is immigration?
A
- individuals move into a population and stay
15
Q
What is emigration?
A
- individuals leave a population and do not return
16
Q
What is the birth rate in humans?
A
- the number of births per 1000 people in a year
17
Q
What is the death rate in humans?
A
- the number of deaths per 1000 people in a year
18
Q
When do populations grow?
A
- when birth and immigration exceed death and emigration
19
Q
When do populations decline?
A
- when death and emigration exceed birth and immigration
20
Q
When do populations remain stable?
A
- when birth and immigration approximately equal death and emigration
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
22
Q
What does exponential mean?
A
- increasing more and more rapidly
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
24
Q
What does environmental resistance cause?
A
- the birth rate/immigration rate to decrease
- and the death rate/emigration rate to increase
25
What happens when a balance is reached?
- the population stabilises at a particular size or number
26
What is the carrying capacity?
- the population density that the environment can support
27
What does the population fluctuate around?
- around the carrying capacity until the environment changes again
28
When does population size fluctuate?
- seasonally and annually
- depending on the resources available
29
What kind of regulation does population size possess?
- population size in an ecosystem is self-regulating
30
What are limiting factors?
- the factors that help to regulate the growth of a population
31
What kinds of limiting factors are there?
- density independent factors
- density dependent factors
32
What are density independent limiting factors?
- 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
33
What are the types of density independent factors?
- physical factors
- catastrophic events
34
What are some examples of density independent physical factors?
- rainfall
- temperature
- humidity
- acidity
- salinity
35
What are some examples of density independent catastrophic events?
- floods
- fire
- drought
- volcanic eruptions
- tsunami
- earthquakes
36
What are density dependent limiting factors?
- factors that have a greater effect when the population density is high
37
What happens when organisms are more crowded (density dependent factors)?
- compete more for resources
- are more easily found by predators
- spread disease and parasites more readily
38
What are some examples of resources that organisms compete for when they are more crowded?
- food
- light
- oxygen
- water
- space
- shelter
39
What is a stable population?
- 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
40
When does an unstable population develop?
- if the population far exceeds the carrying capacity
41
What happens to the habitat of an unstable population?
- 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
42
What do direct methods involve?
- counting every single individual in a population - this is called a census
43
What are the types of methods used to estimate population size?
- direct methods
- indirect methods
44
When can direct methods be used?
- for populations where organisms are large enough to be seen
- where the area in which the animals are being counted is not too large
45
For what kind of individuals can direct methods be used?
- slow moving (e.g.
- stationary (e.g. plants)
- usually stay in a fixed position (e.g. barnacles)
46
What can be used if the area is too large to count every individual at one time?
- aerial photographs can be used to show the whole area in which the population occurs
- helicopters can be used to count larger animals
47
What do indirect methods involve?
- counting a sample number of the population and then using simple calculations to estimate the total size of the population
48
What are some examples of indirect methods?
- quadrat method
- mark-recapture method
49
What does the quadrat method involve?
- 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
50
What is the formula for the total population when using the quadrant method?
[numbers in sample x size of whole habitat] ÷ size quadrat
51
What is the purpose of using a quadrat?
- to enable comparable samples to be obtained from areas of consistent size and shape
52
What is important to do when using quadrats?
- quadrats should be distributed at random
53
Why is random sampling important?
- 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
54
What does the mark-recapture method involve?
- 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
55
What is the formula used in the mark-recapture method?
P = (M x C) ÷ R
56
What does the P symbolise in the mark-recapture method formula?
P = estimated population
57
What does the M symbolise in the mark-recapture method formula?
M = total number of marked animals
58
What does the C symbolise in the mark-recapture method formula?
C = total number of animals caught in the second sample
59
What does the R symbolise in the mark-recapture method formula?
R = total number of animals marked in the second sample (i.e. recaptured)
60
What precautions must be taken for a reliable result in terms of time?
- only a short time should pass between the first and second sampling
- so that no births and deaths can occur
61
What precautions must be taken for a reliable result in terms of repetition?
- sampling should be repeated several times and an average population calculated
62
What precautions must be taken for a reliable result in terms of the actual marking?
- the marking must not damage the individual or affect its movement or behaviour
63
What precautions must be taken for a reliable result in terms of the marked animal?
- the marked animal must mix freely with the rest of the population before a new sample is taken
64
What precautions must be taken for a reliable result in terms of immigration and emigration?
- no immigration or emigration is allowed
- i.e. the population must be closed
65
What is the significance of all living organisms within an ecosystem being interdependent?
- this means that changes in the population size of one species can drastically affect that of another
66
What is predation?
- a biological interaction where one species kills and eats another species
67
What does the role that predators play in their environment do?
- helps to create and maintain greater diversity within an ecosystem
68
How do predators create and maintain greater diversity within an ecosystem in terms of regulation?
- by regulating the abundance and distribution of prey species
- as the predator population increases, the prey population decreases
69
How do predator and prey evolve in relation to one another?
- they evolve together and are part of the same environment
70
How do predators create and maintain greater biodiversity within an ecosystem?
- by increasing the biodiversity of communities by preventing a single species from becoming dominant
71
How do predators create and maintain greater diversity within an ecosystem in terms of genetics?
- by keeping the prey population genetically fit by removing sick, injured and weak individuals
72
How do predators create and maintain greater diversity within an ecosystem in terms of food?
- by providing vital food sources for scavengers
73
What does the feeding relationship between the predator and the prey determine?
- determines the size of the two populations by means of a negative feedback mechanism
74
What happens to the predator population as the prey population decreases due to predator killing?
- the food available for the predators is less
- and so their numbers subsequently decline
75
What happens to the prey when predator pressure is reduced?
- the numbers of the prey can increase once again
- and the cycle goes on
76
What is competition?
- when two or more individuals compete for the same resources that are in short supply
77
What resources to individuals compete over?
- light
- space
- water
- food
- shelter
78
What are the types of competition?
- intraspecific competition
- interspecific competition
79
Between whom does intraspecific competition occur?
- between individuals of the same species
80
What does intraspecific competition include?
- competition for mates as well as basic resources
81
Why is intraspecific competition more intense than interspecific competition?
- because members of the same species have similar habitats and resource requirements
82
Between whom does interspecific competition occur?
- between individuals of different species where the niches in a habitat are very similar
83
What is an ecological niche?
- all the conditions necessary for an organism to survive and reproduce
84
What is needed in order for a population to survive?
- its individuals must survive and reproduce
85
What must individuals do in a population to ensure survival and reproduction?
- tolerate the physical environment (temperature, pH)
- obtain energy and nutrients
- cope with competition
- avoid predators
86
What happens when two species with the same or similar ecological niches occupy the same habitat?
- their ecological niches will overlap to a greater or lesser extent
87
What is specialisation?
- the structural and behavioural adaptations that enable individuals of different species to co-exist
88
What does the competition that arises from overlapping ecological niches result in?
- competitive exclusion
- competitive coexistence
89
When does competitive exclusion occur?
- when one of the two competing species is much more successful than the other
90
When does competitive coexistence arise?
- it arises when two competing species coexist in the same habitat
91
What is resource partitioning?
- 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
What does resource partitioning contribute to?
- the great diversity of species on earth
93
How can resources be partitioned?
- at different times
- in different parts of a habitat
- in different parts of the same plant
94
What is stratification?
- 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
How does light intensity differ in vegetation?
- the intensity of light diminishes as the rays pass through the different layers of forest vegetation
96
How is light partitioned in plants?
- the different layers of vegetation are adapted to photosynthesis in different light intensities
97
How are resources partitioned by giraffes and kudu in woodland savannah areas?
- kudu browse on the lower branches and giraffe on the upper branches
98
What is ecological succession?
- a predictable pattern of gradual change over time in the types of species in a community following a disturbance
99
What are the types of ecological succession?
- primary succession
- secondary succession
100
Where does primary succession begin?
- on sites that have not previously had plants growing on them
- e.g. beaches, ponds, bare rock
101
Where does secondary succession begin?
- in areas where a disturbance removes some or all species but the soil remains
102
What are the characteristics of community structure?
- not static
- determined over time by succession that takes place as a result of certain factors
103
What determines community structure?
- disturbances
- competitive interactions
104
What are the kind of disturbances that influence community structure caused by?
- physical disasters (e.g. storms, floods, fires)
- humans or animals (e.g. abandoned crop field, overgrazed area, logged forest)
- climate change
105
How do disturbances determine community structure?
- 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
What are the competitive interactions that influence community structure?
- competition
- predation
107
What are the stages of ecological succession?
1. Pioneer species stage
2. Intermediate species stage
3. Climax community
108
Where do pioneer species grow best?
- bare ground conditions
- where there is little competition for space and resources
109
What are the features of pioneer species?
- hardy
- establish rapidly
- have spores or seeds that can disperse over long distances
- do now grow in shade
110
Why do pioneer species need to be hardy?
- to withstand extreme variations in temperature and moisture
111
What do pioneer species do?
- prepare the surroundings for later colonists
- by altering the biotic and abiotic environment
112
How do pioneer species prepare the surroundings for later colonists?
- build-up, stabilise and enrich the soil
- alter the amount of light available by providing shade
113
What is an example of a floral pioneer species involved in primary succession?
- lichens
114
How are lichens beneficial in primary succession?
- 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
What plants follow lichens in the pioneer species stage?
- mosses and other simple plants
116
What are examples of faunal pioneer species?
- mites
- ants
- spiders
- small herbivores
- other decomposers such as earthworms
117
When does secondary succession in the pioneer species stage occur?
- when the soil layer thickens
118
What are the pioneer species of a secondary succession?
- 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
Why do ecological conditions change and lead to the intermediate species stage?
- the soil can hold more water and is more fertile
- temperatures are less extreme as there is more shade
120
What happens in the intermediate species stage as the soil builds up?
- 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
What animals become part of the community during the intermediate species stage?
- larger herbivores (hares, small antelope)
- small carnivores (caracal, wild cats)
- snakes
- raptors
122
How do the intermediate species affect the communities?
- they make the communities more structurally complex
123
What is the climax community stage?
- the last semi-stable stage
- endpoint of succession
124
How do climax communities vary?
- large trees in a forest biome
- or grasses and Acacia trees in a Savannah biome
- dwarf, succulent shrubs in succulent karoo biome
125
What are the characteristics of animal species in the climax community?
- most diverse
- include large herbivores and carnivores
126
How is everything in a state of transition?
- future disturbances can cause the species of a community to change
- e.g. higher rainfall
127
What environmental fluctuations determine an endpoint to a community?
- rainfall
- overgrazing
- draining of wetlands
- climate change
- invasion by alien species
128
How does rainfall determine successional endpoints?
- 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
How does overgrazing change a community?
- grazers often choose one grass species, which changes the composition of the climax communities in the grassland biome
130
How does the draining of wetlands affect successional endpoints?
- permanently alters the environments
- resulting in the disappearance of wetland climax species
131
How does climate change affect successional endpoints?
- 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
How does invasion by alien species affect successional endpoints?
- they replace the once dominant species in climax communities
133
What is social organisation?
- the structure of relationships within a group
134
What features must be divided among a group to be socially organised?
- resources
- activities
135
What resources must be divided among a group to be socially organised?
- food
- territories
- nest sites
136
What activities must be divided among a group to be socially organised?
- protection
- other skills like hunting
137
Why is social organisation valuable?
- it improves the survival and reproductive success of an individual
138
What does social organisation make it easier to do?
- avoid being attacked by predators
- find food by hunting collectively
- divide labour among individuals
- find mates
- protect resources
- regulate population size
139
What is the biggest advantage of forming a large group (flocking)?
- the safety of the group is increased by avoiding and defending against predators
140
Why are less prey captured when herds or flocks are formed in terms of awareness?
- with many eyes and ears, the group as a whole is more watchful
- particularly the individuals on the edge of the group
141
Why are less prey captured when herds or flocks are formed in terms of mobbing?
- a large herd or flock can mob a predator?
142
What does it mean to mob?
- to surround and overpower
143
How does the dilution effect work?
- the greater the number of individuals in a group, the greater the survival chances are of the individual
144
How does the confusion and distraction effect work?
- as a predator tries to single out its prey
- the herd scatters in all directions
- confusing the predator
145
How do wild dog packs immobilise prey?
- 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
How does the whole wild dog pack share in the kill?
- the young feed first
147
What happens to wild dogs left behind in the den?
- they are fed on regurgitated meat
148
What is the strict ranking system within African wild dogs?
- 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
What happens to the offspring of African wild dogs?
- 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
What are the benefits of the type of social organisation practised by wild dogs?
- 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
What animals are the most advanced form of social organisation?
- eusocial animals
152
How do eusocial animals live?
- in colonies
153
What are the characteristics of the colonies in which eusocial animals live?
- there is a dominant breeding pair or a single female (queen)
- the non-breeding animals have different tasks to perform
154
What kind of tasks do non-breeding eusocial animals do?
- collect food
- caring for the young
- building, maintaining and protecting the nest
155
Why could eusocial colonies not survive on their own?
- environmental pressures such as shortage of resources
156
What is eusociality?
- a major evolutionary innovation
- which has involved changes in life history, structure and behaviour
157
What are some examples of eusocial animals?
- termites
- ants
- some species of bee and wasp
- the make mole-rat
158
What is a colony?
- a highly organised, integrated unit
159
What does the termite caste system include?
- reproductives
- workers
- soldiers
160
What do the reproductives in the termite caste system include?
- alates
- queen and king
- young reproductives
161
What are alates and what do they do?
- two, winged termites
- appear in the rainy season and mate
- each pair can found a new colony
162
What do the queen and king in a termite colony do?
- 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
What do the young reproductives in a termite caste system do?
- they will either become the new alates
- or supplementary reproductive that can replace the queen and king should they die
164
What do the workers in termite caste systems do?
- 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
What do the soldiers in the termite caste system do?
- develops huge biting or squirting mouthparts
- that help with the defense of the colony
166
How is the ratio of castes in a termite colony regulated?
- the king and queen set a ratio of soldiers to workers and nymphs
167
How have humans been able to reduce environmental resistance and increase the carrying capacity of the world's food-producing regions?
- food production has increased substantially
- methods of treating diseases have improved greatly
168
What has caused the exponential growth of the human population?
- reduced environmental resistance
- increased the carrying capacity of the world's food-producing regions
169
Why has food production increased substantially?
- more land is being cultivated
- improved methods of food production such as using artificial fertilisers to increase the yield of monoculture crops
170
Which two groups can the countries of the world be divided into?
1. more developed countries (MDCs)
2. less developed countries (LDCs)
171
What are the characteristics of more developed countries?
- slow population growth
- high standard of living
172
What are the characteristics of less developed countries?
- rapid population growth
- lower standard of living
173
What is a population pyramid?
- a bar graph that shows the composition, by age and sex, of a nation's population at the time of a census
174
What are the main age/sex groups that a population contains?
- pre-reproductive
- reproductive
- post-reproductive
175
What is age structure?
- the relative numbers of individuals of each age in a population
176
What do the different population pyramid shapes depict?
- a rapidly growing population
- a stable population
- declining population
177
What are the characteristics of a rapidly growing population pyramid?
- high birth rate
- rapid fall in each upward age group due to high death rates
- short life expectancy
- commonly found in LDCs
178
What are the characteristics of a stable population pyramid?
- declining birth rate
- low death rate
- more people living due to old age
- found in MCDs
179
What are the characteristics of a declining population pyramid?
- low birth rate
- low death rate
- higher dependency ratio
- longer life expectancy as found in affluent countries
180
What will happen to the population if the pre-reproductive age group is the largest?
- the population will increase
181
What will happen to the population if the pre-reproductive age group is the smallest?
- the population will decrease
182
What is the growth like in a population with more old, non-productive individuals?
- it will grow more slowly
183
What can population graphs do?
- 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
How can epidemics cause the make-up of a population to change?
- HIV/AIDS causing the deaths of many sexually active young men and women particularly in developing countries
185
How can immigrants cause the make-up of a population to change?
- high proportions of young immigrants being rapidly absorbed
- or losses due to emigration of able-bodied young adults
186
How can war cause the make-up of a population to change?
- losses due to able bodied men fighting wars
187
How can economic crisis cause the make-up of a population to change?
- reduced birthrates during times of economic crisis
