Ecology Exam 2 - Population Ecology

What is a population?

A group of organisms of the same species occupying the same space at the same time.

What are the characteristics of populations?

• Abundance % population density

• Population dispersion

• Age structure

What is abundance and population density?

The number of individuals per an area

What is population dispersion?

The spatial arrangement of individuals relative to each other

What is age structure?

Proportion of individuals in a population belonging to each age class?

Difference between cohort life tables and static life tables?

Cohort life tables follow the fate of a group of individuals born at the same time from birth to death

Static life tables considers survival and reproduction of indiiduvals of known age during single time interval

What is exponential growth and its equation?

A change in size of population with continuous reproduction by a constant propoertion at each instant of time (occurs continuously over any fraction of time). (continous time model)

Nt= N0e^rt

What is geometric growth and its equation?

Change in size of population with discrete reproducitve by a constnat proportion from one discrete time period to the next. (geometric growth occurs in discrete step-by-step intervaks) (discrete time model)

Nt = N0 (lambda) ^t

What is a species?

Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups

Survivorship curves:

Type I survivorship curve - humans, gorillas, some mammals

Type II survivorship curve - birds, squierrls, rodents

Type III survivorship curve - Fish, bugs, plants, invertebrates

What is the demography of a population

Age/stage structure of population and survival, fertility, and other rates associated with those ages or life history stages

5 strategies of natural selection

Frequency of Reproduction

Lifespan

Age and size at maturity

Investment in parental care

Size and number of offspring

Life history main 3 processes:

Growth, Maintenance, reproduction

What is a tradeoff?

An inevtiable compromise between 1 trait any other trait that arises because time energy or materials are devoted to one structure or function can be allocated to another

Stochastity types:

Demographic- random variation in birth and death rates due to chance

Environmental- random variation in the environment that directly affects birth and death rates

Genetic (genetic drift)- Impacts are greatest in small poulations (inbreeding)

What is inbreeding?

more likley to mate with relatives in a small population, whcih can lead to reduced fitness and inbreeding depression

2 reasons why the black-footed ferret almost went exticnt

• Thier main food souce, praire dogs had populations run very low

• sylvatic plague killed ferrets and other organisms in the area

Allee effect is what? Give 2 examples:

When birth rates are lower and mortlaity rates are higher in very small, low-density populations compared to larger ones

• Herd (too few animals means easy pickings)

• Pollination

What would the allee effect look like on a graph?

Like this!

What are 3 negative ecological effects of deer overpopulation

Decrease in certain vegetation populations,

Decrease in other wildlife, such as birds that require vegetaiton that the deer have eaten

Effects on people through the destruction of vehicles, gardens, and other plants

What does exponential growth look like on a graph? What bout logistisc?

Infinite-handle Hockey stick versus stretched out wide af s

What are density-dependent factors?

Competition for food/habitat, disease spread, parasitism,

What are density-independent factors?

Natural disasters, early frost, human impact

Life history traits include: