Chapter 11: Intraspecific Population Regulation Flashcards
Exponential population growth is based on assumptions that ?
- essential resources are not limiting and that the environment is constant
Is exponential growth likely to occur in the real world?
- no
- potential exception: human population
Human Population Growth:
- In 2012 population reached?
- 7 billion
- growing faster than exponential
- not evenly spread out, might be causing some of the issues (resources )
Human Population Growth:
- changes to technology and resources used did what for the population?
- 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
Human Population Growth:
- why have growth rates declined?
- mostly bc having children is costly
- but momentum from large number of young people in developing countries
Human Population Growth:
- why is it difficult to predict human population growth?
- 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
- 1 Population growth is usually limited by the environment:
- In nature, environment is?
- not constant and resources are limited
- 1 Population growth is usually limited by the environment:
- mortality, fecundity, competition etc will change as what changes?
density
- 1 Population growth is usually limited by the environment:
- usually____ rate declines and ___ increases as density increases.
- birth
- mortality
- *enivornment controls how many individuals will be in it
- changes as pop gets more crowded
Reindeer herd on Pribilof Islands, Alaska?
- 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
Carrying capacity?
- max sustainable pop size for particular environmental conditions
Carrying capacity depend on what?
- supply of resources: food, water, space
Carrying capacity is a theoretical idea that is easy/hard to determine for a natural population.
- hard
- but useful concept to include n models of population growth
- *CC can change due to conditions changing with it
Logistic model of growth incorporates?
- 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 )
Logistic model of growth:
- As N approaches K, rate of growth?
- 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
Logistic model of growth
- logistic growth curve showing carrying capacity?
- almost like an S
- K is where it levels off…
Logistic vs Exponential Growth when looking at graphs?
- logistic increases but levels off eventually
- exponential doesn’t stop in terms go growth
- 2 Population regulation:
- population can/can’t grow forever?
can’t
*limits to its resources
L> food, water, land, space,mate, habitats
- 2 Population regulation:
- Interactions occur among members of the population that tend to?
-regulate population size (push it towards an equilibrium)
- 2 Population regulation:
- density dependence?
- response of the population depends on its density. Slows the rate of increase
- 2 Population regulation:
- why is k included in the logistic growth model?
- to add density-dependence
- *rates change depending on how dense it is
- more individuals= more interactions (some good other bad), regulate the population size
- 2 Population regulation:
- In nature, density-dependent mechanisms influence?
- 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
Density vs Independent:
- Not all factors affecting birth and death rates are density-dependent.
- Density-independent ?
- 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)
- 3 Competition:
- A carrying capacity means competition occurs when resource(s) are?
in short supply
- 3 Competition:
- Intraspecific competition?
-competition among individuals of the same species
- 3 Competition:
- Intraspecific competition: - Scramble competition?
- can result in reduction of growth and reproduction of all individuals (equally spread)
- 3 Competition:
- Intraspecific competition: - Contest competition?
- some individuals get enough resources while others denied a share (winners and losers)
- 3 Competition:
- Intraspecific competition: - 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)
- 3 Competition:
- Intraspecific competition: - Interference competition?
- individuals directly interact and prevent others from occupying a habitat or accessing resources
- 4 Effects on Growth and Development :
- when density increases, individuals in scrabble competition get ___ food. This ___ growth and ___ reproduction.
- less
- reduces
- inhibits
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
- 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,
- 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
- 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
- 8 Dispersal can be density-dependent:
- some animals instead of coping with stress will?
leave
- 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
- 8 Dispersal can be density-dependent:
- dispersal?
- how far you spread offspring (or individuals relocating)
- 9 Effects of Social Behaviour:
- Intraspecific competition can be expressed in?
- social behaviour
- 9 Effects of Social Behaviour:
- Mechanism to limit number of animals ???
- living in a particular habitat, having access to a common food supply, reproducing
- 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
- 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
- 10 Territoriality:
- some species defend areas within?
their home range (territories
- 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.
- 10 Territoriality:
- can this regulate populations?
- yes
- limits reproduction if excess of individuals of reproductive age.
- 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
- 10 Territoriality:
- example?
- when individuals are removed, new pairs take up territories right away
- 11 Plants can capture Space:
- Plants are not ?
- territorial but do capture space and exclude others from it
- 11 Plants can capture Space:
- zones of resource depletion associated with?
- canopy and root systems
- 11 Plants can capture Space:
- This competition can even occur through?
the release of organic toxins
- 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
- 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
Development of ideas about density dependence vs independence:
- Historically, two opposing view points in ecology about population regulation (centred on insects)
- Two schools are?
- Biotic school of regulation
2. Climate school of regulation
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
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
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
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.
