Chapter 11: Intraspecific Population Regulation Flashcards
1
Q
Exponential population growth is based on assumptions that ?
A
- essential resources are not limiting and that the environment is constant
2
Q
Is exponential growth likely to occur in the real world?
A
- no
- potential exception: human population
3
Q
Human Population Growth:
- In 2012 population reached?
A
- 7 billion
- growing faster than exponential
- not evenly spread out, might be causing some of the issues (resources )
4
Q
Human Population Growth:
- changes to technology and resources used did what for the population?
A
- dev of agriculture increased quantity and predictability of resources. Change to permanent villages. (not farming yourself)
- Industrial revolution: animal and human labour replaced by machines fuelled by coal. Change to urban society.
- Demographic transition: reduced mortality due to better nutrition, personal hygiene, waste disposal and control of disease
- **all allowed for our pop to take off
5
Q
Human Population Growth:
- why have growth rates declined?
A
- mostly bc having children is costly
- but momentum from large number of young people in developing countries
6
Q
Human Population Growth:
- why is it difficult to predict human population growth?
A
- diseases, resources (not evenly spread out), conflicts (war) etc
- hard to predict where (the change) is going to happen, bc resources are going to change quickly
7
Q
- 1 Population growth is usually limited by the environment:
- In nature, environment is?
A
- not constant and resources are limited
8
Q
- 1 Population growth is usually limited by the environment:
- mortality, fecundity, competition etc will change as what changes?
A
density
9
Q
- 1 Population growth is usually limited by the environment:
- usually____ rate declines and ___ increases as density increases.
A
- birth
- mortality
- *enivornment controls how many individuals will be in it
- changes as pop gets more crowded
10
Q
Reindeer herd on Pribilof Islands, Alaska?
A
- increasing then boom it crashes (fighting, disease etc) (1940ish)
- we don’t want this to happen to our moose so we regulate it
- not a typical graph..most species do not drop dead like this
11
Q
Carrying capacity?
A
- max sustainable pop size for particular environmental conditions
12
Q
Carrying capacity depend on what?
A
- supply of resources: food, water, space
13
Q
Carrying capacity is a theoretical idea that is easy/hard to determine for a natural population.
A
- hard
- but useful concept to include n models of population growth
- *CC can change due to conditions changing with it
14
Q
Logistic model of growth incorporates?
A
- incorporates carrying capacity, K
dN/dt = rN (1-N/K)
- Two components: rN which is the original exponential term and
- 1-N/k, also can be written as (K-N)/k, which reduces population growth as the population size approaches k
- d= change
- rate size ( slow down component/density component )
15
Q
Logistic model of growth:
- As N approaches K, rate of growth?
A
- decreases
ex: K= 100
If N= 10
(1-N/k)= 0.90
but if N=99, (1-N/K)=0.01 and there will be virtually no growth
16
Q
Logistic model of growth
- logistic growth curve showing carrying capacity?
A
- almost like an S
- K is where it levels off…
17
Q
Logistic vs Exponential Growth when looking at graphs?
A
- logistic increases but levels off eventually
- exponential doesn’t stop in terms go growth
18
Q
- 2 Population regulation:
- population can/can’t grow forever?
A
can’t
*limits to its resources
L> food, water, land, space,mate, habitats
19
Q
- 2 Population regulation:
- Interactions occur among members of the population that tend to?
A
-regulate population size (push it towards an equilibrium)
20
Q
- 2 Population regulation:
- density dependence?
A
- response of the population depends on its density. Slows the rate of increase
21
Q
- 2 Population regulation:
- why is k included in the logistic growth model?
A
- to add density-dependence
- *rates change depending on how dense it is
- more individuals= more interactions (some good other bad), regulate the population size
22
Q
- 2 Population regulation:
- In nature, density-dependent mechanisms influence?
A
- birth and death rates
- direct effects of resource availability or other factors (disease and parasites)
*realistic graph shows birth rate declines as the population size increases and death rates increase as population increases
at carrying capacity they are=? / intersect
23
Q
Density vs Independent:
- Not all factors affecting birth and death rates are density-dependent.
- Density-independent ?
A
- if the proportion of population affected by an environmental factor is not influenced by density
- *weather, temperature, precipitation are all density independent (not a dependent factor like birth and death rate - not affected)
24
Q
- 3 Competition:
- A carrying capacity means competition occurs when resource(s) are?
A
in short supply
25
11. 3 Competition:
| - Intraspecific competition?
-competition among individuals of the same species
26
11. 3 Competition:
- Intraspecific competition:
1. Scramble competition?
- can result in reduction of growth and reproduction of all individuals (equally spread)
27
11. 3 Competition:
- Intraspecific competition:
2. Contest competition?
- some individuals get enough resources while others denied a share (winners and losers)
28
11. 3 Competition:
- Intraspecific competition:
3. exploitation competition?
- if competing individuals don't interact directly but change level of resource for others
ex: tree roots(might spread out and absorb all the water - exploiting this resources ahead of someone else)
29
11. 3 Competition:
- Intraspecific competition:
4. Interference competition?
- individuals directly interact and prevent others from occupying a habitat or accessing resources
30
11. 4 Effects on Growth and Development :
| - when density increases, individuals in scrabble competition get ___ food. This ___ growth and ___ reproduction.
- less
- reduces
- inhibits
31
11.4 Effects on Growth and Development:
-Intraspecific competition:
ex: tadpoles?
L> high vs low density
- high density=slower growth, longer tadpole phase, lower change of transformation to frog, smaller size frog.
* * at low density they grow much faster
32
11. 5 Competition can reduce survival:
| - ex: horseweed?
- horseweed planted at high density
- competition resulted in mortality of many seedlings
- average size of surviving seedlings increased
- self thinning
* ** at high density they are small, as density is reduced they grow faster/ more weight. Competition can change growth rate, reproduction rates and survival,
33
11. 6 Competition can affect reproduction:
| - Harp seals?
- in harp seals, onset of sexual maturity is related to body weight
- occurs earlier when the population size is lower
* *if they don't grow fast enough it delays the mount of babies they can have.
* *results in density-dependent fertility of harp seals : number they can produce will drop (population problem - producing fewer as they get more dense) --> population regulation
34
11. 7 High density is stressful:
- ___ contacts increase
- Stress may trigger?
- Pheromones?
- aggressive
- stress may trigger hormonal changes that suppress growth and reproduction as well as the immune system
- pheromones( chemical signals): can encourage or discourage reproduction in rodents.
* *so dense that they re giving off hormonal singles , increasing aggression
35
11. 8 Dispersal can be density-dependent:
| - some animals instead of coping with stress will?
leave
36
11. 8 Dispersal can be density-dependent:
| - usually ___ driven out by ___ aggression.
- sub-adults
- adult
* most die but some find a new suitable area
* usually doesn't regulate population size
* does contribute to population expansion and persistence of local populations
37
11. 8 Dispersal can be density-dependent:
| - dispersal?
- how far you spread offspring (or individuals relocating)
38
11. 9 Effects of Social Behaviour:
| - Intraspecific competition can be expressed in?
- social behaviour
39
11. 9 Effects of Social Behaviour:
| - Mechanism to limit number of animals ???
- living in a particular habitat, having access to a common food supply, reproducing
40
11. 9 Effects of Social Behaviour:
| - what can play a role in population regulation if it affects reproduction and survival in a density dependent way?
- social dominance
41
11. 9 Effects of Social Behaviour:
| - example: Wolf packs and social dominance
- strict social hierarchy with only one breeding pair in the pack ( the alpha male and female)
- if food is limited, individuals may be expelled (priority of food goes to the alpha pair)
- when density of wolves is low, wolves leave pack and establish their own packs in unoccupied habitats
42
11. 10 Territoriality:
| - some species defend areas within?
their home range (territories
43
11. 10 Territoriality:
| - Benefits of what must outweigh costs of what?
- benefits of sole access to resources in territory must outweigh costs (energy, time) of having a territory.
44
11. 10 Territoriality:
| - can this regulate populations?
- yes
| - limits reproduction if excess of individuals of reproductive age.
45
11. 10 Territoriality:
| - explain areas
- size of home ranges and territories indicator of carrying capacity
* *little factors that come into play for regulating populations apart form birth and death rates
46
11. 10 Territoriality:
| - example?
- when individuals are removed, new pairs take up territories right away
47
11. 11 Plants can capture Space:
| - Plants are not ?
- territorial but do capture space and exclude others from it
48
11. 11 Plants can capture Space:
| - zones of resource depletion associated with?
- canopy and root systems
49
11. 11 Plants can capture Space:
| - This competition can even occur through?
the release of organic toxins
50
11. 12 Density-Independent Influences:
| - Many factors can influence the abundance of individuals in a population. Some not density dependent and so can't?
- regulate a population (which involves feedback)
exL temperature, precipitation , natural disasters
**may still limit pop growth
51
11. 12 Density-Independent Influences:
| - ex: heavy snow fall and deer prediction?
- heavy snow you can predict fewer deer born next year....population is going to decline
52
Development of ideas about density dependence vs independence:
- Historically, two opposing view points in ecology about population regulation (centred on insects)
- Two schools are?
1. Biotic school of regulation
| 2. Climate school of regulation
53
Development of ideas about density dependence vs independence:
- Historically, two opposing view points in ecology about population regulation (centred on insects)
1. Biotic school of regulation??
- felt that population size was relatively stable and insect populations were controlled by parasites, predators or competition ...biology drives it
54
Development of ideas about density dependence vs independence:
- Historically, two opposing view points in ecology about population regulation (centred on insects)
2. Climate school ?
- viewed populations as unstable and felt that weather determined abundance e.g. environmental/ physical environment drives it/more important
* if variable climate then you may argue physical environment has a bigger effect
* competition , high number of species = biology
55
Development of ideas about density dependence vs independence:
- controversy for many years
- Two perspective eventually integrated
- Now believed that ___ are in usually favourable to species, changes in abidance primarily result of density dependent process.
- favourable
56
Development of ideas about density dependence vs independence:
- controversy for many years
- Two perspective eventually integrated
L> In unfavourable environments?
- changes in abundance are primarily the result of density independent processes.
