UNIT 3 - Chapter 4 - Population Dynamics

Question 1

Answer 1

Examples with labels of Logistic Growth Curves

Question 2

Density-Dependent Mortality
&
Density-Dependent Fecundity

Answer 2

INTRASPECIFIC COMPETITION
&
THE 4 TYPES OF THIS COMPETITION

For 2a)b) – Higher density can be stressful for species. Aggressive or antagonistic interactions can occur. In animals, these interactions may cause stress and triggor hormonal changes that may:
1. suppress growth
2. curtail reproduction (decreased births)
3. delay sexual activity
4. suppress immune system (more vulnerable to disease – more mortality in both young and adult)
5. It can also cause DISPERSAL from the population. Dispersal happens anyways, regardless of density, but is often positively correlated with population density. A lack of resources can cause dispersal of the sub-adults that are driven out by adult aggression.

Question 3

1. DENSITY-DEPENDENT GROWTH

Answer 3

Question 4

2nd one: DENSITY-DEPENDENT MORTALITY:

Answer 4

3rd one: DENSITY-DEPENDENT affects on FECUNDITY:

Question 5

Home Range & Territories

Answer 5

Allee effect: a phenomenom where the individuals have a higher probability of survival or reproductive success…when population density is higher!

Pop density declines….birthrate declines

Question 6

Density INDEPENDENT FACTORS:
(6 of them)

*Density-independent causes, on the other hand, are external factors that affect population size regardless of population density.

INFLUENCE birth + death…not density

Answer 6

Density-independent factors are environmental factors that affect population size or growth regardless of the population’s density.

1. Climate and Weather Events: Extreme weather events such as hurricanes, droughts, floods, or severe temperature fluctuations can impact population size by directly causing mortality or affecting reproductive success.
2. Natural Disasters: Large-scale natural disasters like earthquakes, volcanic eruptions, wildfires, or tsunamis can have profound effects on population size, causing widespread mortality and habitat destruction.
3. Habitat Destruction: Anthropogenic activities or natural processes that result in the loss or degradation of habitat, such as deforestation, habitat fragmentation, or pollution, can significantly impact populations irrespective of their density
4. Environmental Pollution: Pollution of air, water, or soil with toxins, chemicals, or pollutants can have detrimental effects on populations, leading to reduced reproductive success, increased mortality, or impaired development.
5. Availability of Resources: Changes in the availability of essential resources, such as food, water, or nesting sites, can impact populations. For example, a sudden decrease in food availability due to overexploitation or disruption of natural food webs can lead to population declines.
6. Disturbances: Natural disturbances like wildfires, landslides, or avalanches can have significant impacts on populations, resulting in mortality or habitat alteration that affects population size and distribution.

Question 7

OVERSHOOT :

a situation where a population temporarily exceeds the carrying capacity of it’s environment (carrying capacity being the maximum population size that an ecosystem can sustainably support over the long term)

Answer 7

Question 8

Density-dependent processes play a significant role in driving population cycles. As population density increases, the effects of competition for resources, predation, disease, or other density-dependent factors intensify. This leads to decreased reproductive success, increased mortality, and overall population decline. As the population declines, competition eases, and resources become more available, allowing the population to rebound and begin another phase of growth. This cyclical pattern repeats as population size oscillates

Answer 8

Density-INdependent causes, on the other hand, are external factors that affect population size regardless of population density. AFFECT but do not REGULATE. These causes can include environmental conditions, weather events, natural disasters, or resource availability. These factors can influence population cycles by directly impacting birth rates, death rates, or habitat suitability, regardless of the effects of competition or density-dependent regulation.