Population Ecology Pt.2

There are many sex ratio types, why do we have so many?

When looking into management, you need to know who is producing and at what age are they reproducing.

What is primary sex ratio?

The ratio at fertilization (50/50)

What is secondary sex ratio?

Ratio at birth

What is tertiary sex ratio?

Ratio in recruits (juveniles)

What is quaternary sex ratio?

Ratio in adults

What animals do not fit these sex ratios?

Nine-banded armadillos and some species of turtles.

What is monogamy and how does that affect sex ratio?

It is the pair bonding of a female and male for one breeding season or longer. This makes to where the population is limited by the lowest proportion of males or females.

What is polygyny and how does it affect sex ratios?

This is when one male has multiple females (harem). This affects the sex ratio by it favoring females, since you need only one male but multiple females in order to reproduce. Ex) elk, waterbuck, prairie chickens, and fruit eating bats

What is polyandry and how does it affect sex ratios?

This is one female and multiple males. This affects the sex ratio by favoring males.

What is promiscuity and how does it affect sex ratios?

This is when either sex has multiple sex partners. This could skew the sex ratio towards females.

What is biotic potential when it pertains to sex ratios?

Biotic potential (reproductive potential) is the maximum reproductive capacity of an organisms or population if resources are limited.

What factors can influence biotic potential?

The age at which they reproduce, the frequency at which reproduction occurs, the average number of offspring produced each time, the length of the organisms reproductive life span, & the death rate of individuals.

What is age ratio?

The statistical study of the characteristics of populations such as size, growth, density, distribution, and vital statistics.

Why is age ratio important in a population?

If you know age ratio, you can determine in what direction the population is going.

What is RLF, replacement level fertility?

This refers to when adults have enough offspring to replace themselves.

What is the RLF number in humans?

At least two, since you need one to replace mom and one to replace dad. But since you dont really know if both are going to make it to reproduce on their own usually you want three just in case.

What is genetic structure?

This refers to any pattern in the genetic makeup of individuals within a population. limited information though since it is costly to get and constant changes. (evolution)

What is vagility?

The degree to which an organism or taxon can or does move or spread within an environment.

What is natal philopatry?

The continued residence on the natal home range.

What is panmictic?

A population without structure or restrictions regarding mating, mate with whoever is closest to you.

What is an example of genetic structure and how geographic range can have individuals more closely related than randomly selected from the general population?

Giraffes, there are six genalogically distinct lineages of giraffes in Africa. So little interbreeding among them since they are so close. So if you get a giraffe from all the up north and one from the south of Africa, they would not be as related as you think since they are geographically isolated and so are the genes that have been passed down through generations of breeding.

What are the functional attributes of a population?

Turnover rates, rate of growth, size and density changes, homeostatic regulatory mechanisms, and adaptational mechanisms.

What are the four factors when it comes to population dynamics?

Natality, Mortality, Immigration, Emmigration

What is natality?

The inherent ability of a population to increase in numbers, reproductive or biotic potential.

What is primary natality?

Fecundity-in utero young/total female adults

What is net natality?

Total female young/total female adults

What is refined natality?

Total young/total female adults

What is Gross Natality?

Total female young/total adults

What is Crude Natality?

Total young/total adults

How is natality used when looking at a population?

Natality not only gives an indication of short term yield, but can also be used to predict long term productivity by a species.

What does it mean when a species has an ‘r’ reproductive strategy?

They reproduce at high rates, their life span is usually short, reproduction starts at a young age, high fecundity, Iteroparity, unstable environments.

What does it mean when a species has a ‘K’ reproductive strategy?

They have a low rate of reproduction, long life spans, reproduce at a later stages in life, low fecundity, semelparity, stable population density and stable environments

What are some causes of mortality in populations?

Predation, hunting, competition, accidents, toxins, pollution, disease, and parasitism.

When is mortality usually measured?

Around the same time of year annually, impacts populations at different times of the year. May be constant in effect or sporadic, primarily related to natural selection on a population.

If your objective as a wildlife manager was to abridge the impact of mortality on a population what would you do?

You first want to find out the seasonal mortality during periods of stress.

What would be the solution for bridging the gap of mortality during seasonal mortality?

Keep seasonal low in winter, manipulate by hunting, if mortality is assessed for each age class manager can develop a harvest plan based on this data

What are life tables and how do they help wildlife managers?

They are a way to represent mortality and survival statistics for a population, this helps W.M. by predicting the future populations growth and density.

Why did human demographers and actuaries make life tables?

They wanted to measure the death rate in a group of subjects during a period of time.

What is a cohort/dynamic life table?

A cohort life table follows the animals throughout their entire lives, so from birth to death. It is a group of individuals that were born during the same time interval.

What is a current or time specific/static life table?

This is age distribution data collected from a cross section of the population at a given time. So mortality/ harvest data/ Sample over time and see change in population

Why is cohort/dynamic life tables hard in natural populations?

Because cohort follow animals/populations from birth to death. It is hard to do that with natural populations since they are ever changing and sometimes always moving.

What is a Type I survivorship curve?

This is when an animal has a late loss. So the organisms has few offspring, substantial parental care, convex shape curve, and low mortality until old age

What animal has a Type I curve?

Elephants have a type one curve and also humans.

What is a Type II survivorship curve?

This is constant loss. So it is a straight line going down the graph. This means that the species has an equal change of dying at any age. w

What species have a type II survivorship curve?

Multiple bird species have a type II survivorship curve.

What is a Type III Survivorship curve?

Early loss in the species/organism, this means that they have high mortality early on and most offspring die.

What type of species have a Type III survivorship curve?

Typically most plants and animals that do not receive parental care.

What are density independent factors?

Factors that limit the population regardless of density. So floods, pollution, weather, fires, and pesticides.

What are density dependent factors?

Factors that depend on the density of the population. So overcrowding, predation, competition.

What is exponential population growth?

Only occurs during special conditions. It looks like a J.

Where can you observe expontential growth models?

In populations that observe boom and bust cycles. so rapid growth and then a massive die off. these cycles can be short lived rapidly reproducing species.

What is logistic growth model?

It is an empirical description of how a population tend to grow when environmental conditions are not optimal.

What is reaction time lag?

It is when a change in the environment and a corresponding change in the rate of population growth, usually making the growth rate negative

What is reproduction time lag?

This is when the length of time for gestation and a corresponding change in the rate of population growth, so this can also make the growth rate negative.