Population Ecology Flashcards
(92 cards)
1
Q
What is Ecology?
A
Ecology is the study of the mutual interactions among living organisms & the environment in which they live.
2
Q
What is Population Ecology?
A
Population ecology is the part of ecology that focuses on the factors influencing population size, growth rate, growth forms & distribution of individuals within a population.
3
Q
Define individual:
A
A single organism that forms part of a species.
4
Q
Define Species:
A
A group of organisms with similar characteristics that produce fertile offspring.
5
Q
Define population:
A
A group of organisms of the same species that are found in a particular area & can be crossbred easily.
6
Q
Define community:
A
A group of populations occurring in a particular area. (e.g: lion, zebra, giraffe, rhino populations in Kruger)
7
Q
Define ecosystem:
A
A unit of plant and animal communities (biotic) in interaction with each other as well as with non-living (abiotic) factors in a particular area.
8
Q
Define Biosphere:
A
The biosphere, aka the ecosphere, is the worldwide sum of all ecosystems.
9
Q
Define habitat:
A
The specific environment in which a plant or animal species normally occurs.
10
Q
Define Ecological Niche:
A
The role a species plays in a community.
(e.g: lions fill the role of hunting large herbivores)
11
Q
Define population size:
A
The total number of individuals in a population.
12
Q
Define population density:
A
The number of individuals per unit area.
(e.g: 10 sheep per hectare)
13
Q
Define natality:
A
Birth rate of a population.
14
Q
Define Mortality:
A
Death rate of a population.
15
Q
Define immigration:
A
The one-way movement of organisms into an area.
16
Q
Define emigration:
A
The one-way movement of organisms out of an area.
17
Q
Name factors positively affecting population size:
A
-Natality (expressed in number of births per thousand individuals per year)
-Immigration
18
Q
Name factors negatively affecting population size:
A
-Mortality (expressed in number of deaths per thousand individuals per year)
-Emigration
19
Q
What are population growth forms?
A
Growth forms are distinctive growth patterns that different populations have.
20
Q
What are the different types of growth forms?
A
-Geometric (J-shaped) growth form.
-Logistic (S-shaped) growth form.
21
Q
Describe the J-shaped growth form & why it occurs:
A
-Geometric or exponential growth.
-It occurs when a population has unlimited resources (e.g: food, water, space & no predators)
-The ideal environmental conditions result in maximum growth & population size increases rapidly.
22
Q
What are limiting factors?
A
Limiting factors are factors that prevent unlimited growth in a population which would exceed its maximum growth rate.
23
Q
Give six examples of limiting factors:
A
-Shortage of food & water.
-Shortage of living space.
-Shortage of shelter.
-Predation.
-Diseases & parasitism.
-accumulation of toxins.
24
Q
What is environmental resistance?
A
Accumulation of limiting factors that lower population growth.
25
Define carrying capacity:
The number of individuals that the reserve can actually support. (equilibrium phase)
26
Describe the S-shaped growth forms & why they occur:
-An exponential graph that flattens out to the carrying capacity.
-It occurs due to the limiting factors transforming the J-shaped curve into the S-shaped graph.
27
Describe the different phases of an S-shaped graph & where they are located on the graph:
1. Lag phase (lowest part before exponential growth)
2. Accelerating phase ( when graph reaches peak growth)
3. Decelerating phase ( when graph begins to decelerate)
4. Equilibrium phase ( when graph reaches carrying capacity)
28
Explain the lag phase:
-Initially, the population grows slowly
-Due to population acclimatizing & adapting to environments.
-Become sexually mature & seek mating partners.
-It takes time for offspring to be produced.
29
Explain Accelerating growth phase:
-Population grows rapidly and reaches its maximum growth rate.
-This is due to little to no environmental resistance.
-Natality is higher than mortality.
30
Explain decelerating growth phase:
-The population decreases in growth rate.
-This is due to environmental resistance.
-Natality is higher than mortality.
31
Explain equilibrium phase:
-Population now reaches the carrying capacity of the environment.
-Population stabilizes around carrying capacity.
-Natality and mortality are almost equal.
32
Once a population reaches the carrying capacity, how does the graph look?
-The population will fluctuate between narrow boundaries. (looks like a sine graph)
-This is due to slight changes in environmental resistance.
33
Define a stable population:
A stable population is when population numbers fluctuate around the carrying capacity.
34
Define an unstable population:
-An unstable population is when population numbers far exceed carrying capacity.
-This leads to a destroyed habitat, which decreases the total carrying capacity of environment.
35
How does the graph for an unstable population look:
-The population far exceeds the carrying capacity, leading to ecological overshoot.
-The carrying capacity would start to lower & then a massive exponential decline in population occurs.
36
What are the two different types of limiting factors?
- Density-dependent factors.
-Density-independent factors.
37
Explain density-dependant factors:
-They are factors that increase as population increases.
-An increase in population results in:
- greater demand for food
- decrease in living space
- shortage of shelter
- increased predation
- easier spread of disease
- an accumulation of waste
38
Explain density-independent factors:
-Factors that regulate population size regardless of density/size.
-These factors include:
- Extreme change in temperature.
-natural disasters.
-These factors will usually cause drastic decrease in population size. -> population could recover if the habitat is not destroyed.
39
Give an example of no limiting factors and why this occurs?
-Invasive alien species.
-It occurs due to:
- few natural enemies
- high reproduction rate
- long-lived
- good dispersal
- pioneer species
- generalists
40
Why are alien species bad?
-Crowd out or replace native species
-Can severely damage ecosystem health.
-Harm human activities (e.g: agriculture, forestry...)
41
What are the two categories of population size determining & what determines which category to use?
-Direct method
-Indirect method
-The method is determined by:
- size of organisms
- The mobility of the organisms.
42
Explain the direct method:
A total count of all individuals is done.
- This is called a census.
43
Name different direct census methods:
-Direct contact counting (small organisms & humans)
-Direct counting from vehicle/plane (large organisms)
-Counting from aerial photographs.
44
Explain indirect Methods:
-Only part of the population is counted.
-The count is used to estimate the population size by statistical calculations.
45
Name the different types of indirect methods:
-Mark-Recapture
-Quadrat technique
46
Explain the Mark-recapture technique:
Mark-Recapture aka Lincoln Peterson
1. Demarcate an area
2. Num of individuals are caught, counted, and marked.
3. Marked individuals are released.
4. Market individuals are given sufficient time to mix.
5. Catch another group and count marked individuals.
6. Estimate size of population using a formula:
47
What is the formular used in the mark-recapture technique?
P = (m*s) / t
p - estimated population size
m - total number of individuals - sample 1
s - total number of individuals - sample 2
t - number of marked individuals - sample 2
48
How do you make mark-recapture more accurate?
Repeat and average results to make it more accurate.
49
How do you validate the mark-recapture method?
To validate:
- marking must injure individuals
- marks must be clearly visible
- marking doesn't affect movement or behaviour of individual
- closed population (no emigration/ immigration)
- time period mustn't allow for natality or mortality
50
Explain the quadrat technique:
-An indirect method for stationary creatures.
-A quadrat is usually metal, wood or plastic square of a known size.
-A larger area id demarcated and surface area is determined.
-Quadrat is randomly placed in demarcated area & organisms inside frame are counted.
-Process is repeated many times.
-Average number of individuals per quadrat is calculated using a formula.
51
Explain the formular used in the quadrat technique:
Pop. size = (AQ) (SA / SAQ)
AQ = Average number of individuals per quadrat.
SA = surface area of area.
SAQ = surface area of quad.
52
How is the quadrat technique validated?
- The exact number of organisms in each quad must be known
- Organisms musn't move
- Surface area of quad is known
- Surface area of demarcated area is known
- Quad is placed randomly & in demarcated area.
53
Name the different types of organisms in an ecosystem:
-Producers
-Consumers
-Decomposers
54
Define producers:
-Producers are green plants that photosynthesize & produce carbohydrates.
-Autographic
-Form the basis of food web.
55
Define consumers:
-Consumers have to eat/absorb other organic matter (plants/animals) for food/energy.
-heterotrophic
56
What are the different types of consumers?
-Primary (eat plants)
-Secondary (eat animals that eat plants)
-Tertiary (eats animal that eats animal)
57
Define decomposers:
-Decomposers are bacteria and fungi that feed on and break down dead organic matter.
-Essential for nutrient cycling in the ecosystem.
58
Define symbiotic relationships:
-Close, long-term interaction between the different species.
59
What are the different types of symbiotic relationships?
-Mutualism
-Commensalism
-Parasitism
60
Explain mutualism:
-Association between organisms of two different species in which each benefits.
-Mutualism arrangements are likely to occur between organisms with widely different living conditions.
61
Explain commensalism
-A relationship between individuals of two species in which one benefits by obtaining food and the other by receiving food/protection.
62
Explain parasitism:
-An association between two different species, where the symbiotic benefits and the host is harmed.
63
List characteristics of predators:
-Agility
-Speed
-Stealth
-Increased sense of smell and sight
-Sharp teeth, claws & beak
-good camouflage
64
List characteristics of prey:
-Herding
-Good camouflage
-Speed
-Warning coloration (Aposematism)
-Defense mechanisms
65
Define coevolution:
When two species change and evolve over time in response to one another.
66
What is intraspecific vs inter-specific
Intraspecific -> competition within a species.
Inter-Specific -> competition between species.
67
Define compeditative exclusion:
If two species with the same niche coexist in the same ecosystem, then one will be excluded from community due to intense competition.
68
What is resource partitioning?
- Resource partitioning is a way of reducing competition.
69
Give examples of resource partitioning:
Plants -> different root depths tap which into different water sources
Seabirds -> feed at different water levels due.
70
Define ecological succession:
-Community changes over time
-The sequence of organisms that occupy a new habitat
(primary succession) or a disturbed habitat (secondary succession)
71
Give an example of primary succession:
A rockfall occurs, revealing new soil.
- Species will move into previously uninhabited areas.
72
Give an example of secondars succession:
Land recovering after fire.
- happens much more quickly than primary succession.
73
Define social organisation:
The way individuals live & interact within a group
74
Why does social organisation occur?
-Anti-predation strategies.
-Successful hunting strategy/finding food.
-Division of tasks (eusocial animals)
-Finding mates.
-Protect resources.
-Regulate population size.
75
Why would animals hunt in a pack?
-Quicker & easier to catch prey.
-Less threat from competing predators.
-Safety in numbers from other predators.
-Sufficient resources for all.
-Many eyes & ears.
-Safety for young & females.
76
Define Eusocial animals:
-Eusocial animals are truly social animals.
-Divide labour -> breeding pair, non-breeding animals will have different tasks.
77
Why do eusocial animals occur?
They occur because of environmental pressures being so harsh that individuals can't survive on their own.
78
How has the human population increased over the years & why?
-Grown in a J-shape or exponential way.
- due to advances in medicine and the green revolution ( increased agricultural productivity)
-Also due to a decrease in mortality & increased life expectancy.
79
What advances in medicine has helped increase human populations?
-Improved methods of treating disorders.
-Development of vaccines against infectious diseases.
-Antibiotics
-Cancer treatment
80
How has the green revolution increased human populations?
-Disease-resistant food crops
-Use of artificial fertilizers
-Effective, mechanised farming
-GMO's
81
What is happening to the human population growth currently?
The graph is becoming logistic or S-shaped, which shows a decrease in population growth.
82
What are the three age-categories?
1. Pre-reproductive age
2. Reproductive age
3. Post-reproductive age
83
What is gender distribution?
Gender distribution is the proportion of males to females.
84
What is an ecological footprint?
-EF measures the amount of biologically productive land and water required to regenerate the resources consumed by the human population.
-Measures the human demands placed on the environment.
85
Define biocapacity:
The amount of land and water available on earth.
86
List biologically productive area:
-Arable land.
-Grazing.
-Forests.
-Build-up areas.
-Fossil fuel/mining areas.
-fishing waters.
87
What is EF measured as & how can you find environmental sustainability?
-Ef is measured in global hectares (gha = 100m*100m)
-You can find environmental sustainability by comparing EF with Earth's biocapacity.
88
Define ecological overshoot:
Ecological overshoot is when natural resources are used up faster than they can be replenished.
89
What are the consequences of ecological overshoot?
-Collapse of fish stocks.
-Decreased forest cover.
-Depletion of freshwater sources.
-Accumulation of waste & pollution resulting in climate change.
90
Describe the stable gender distribution graph:
- More square shape
- Base is same width as reproductive age.
- lower natality and lower mortality.
91
Describe the rapid gender distribution graph:
- Wide base, narrow top
- High birth rate and high death rate
92
Describe the negative gender distribution graph:
- Base is narrower than reproductive stage
- Low natality, stable mortality, increased emigration
