Comprehensive Guide to Life History, Population Ecology, and Community Interactions in Biology

Life History

The schedule of an organisms growth, development, reproduction and survival

- Cycle of birth, growth, reproduction and death

Fecundity

The # of offspring produced by an organism per reproductive episode

Parity

The # of reproductive episodes an organism experiences

Parental Investiment

The amount of time and energy given to an offspring by its parents

Longevity

The lifespan of an organism aka like expectancy

Plant Life History

A plant species cycle of birth, growth, reproduction and death

- How a plant grows and develops

- Annual vs. perennial plants

- # of offspring (seeds)

- Size of offspring

Offspring # vs. offspring size

1. Life history traits contribute to reproductive success but also influence evolutionary fitness

2. Life histories vary with respect to environmental factors, suggesting that life history traits are molded by natural selection

3. The # of offspring that parents can successfully bear is correlated to "food supply"

Fast Life History Traits

- Greater # of offspring

- Shorter life spans

- Faster growth

- Earlier reproduction

- Earlier sexual maturation

- Smaller parental investment

Slow Life History Traits

- Fewer offspring

- Longer lifespan

- Slower growth

- Delayed reproduction

- Later sexual maturation

- Greater parental investment

Population Ecology

How does a population change overtime

Why do populations change over time

Population

A group of the same species that is interacting

Spatial Structure

The pattern of density and spacing of individuals in a population

5 Important Characteristics of Population Distributions

1. Geographical Range

2. Abundance

3. Dispersal

4. Density

5. Dispersion

Geographical Distribution

Determined by abiotic and biotic factors

Ecology Niche Modeling

The process of determining the suitable habitat conditions for a species

Abundance

The total number of individuals in a population that exists within a defined area

Dispersal

The movement of individuals from one area to another

Density

In a population, the number of individuals in a quantified area or volume

Dispersion

The spacing of individuals with respect to one another within the geographic range of a population

Test for Dispersion

Index of dispersion test - Chi-squared test

Dispersion Index

1 = Random

>1 Aggregated

<1 Regular

Deomgraphy

The study of factors that determine the size and structure of a population over time

4 Proccesses of Demography

- Immigration

- Emigration

- Birth

- Death

Life Tables

Summarizes the probabilities that an age class or cohort will survive and reproduce in any given year over the individual's lifetime, based on survivorship (Ix)

Age Class

Infancy- childhood - early reproductive - late reproductive - post reproductive

X

Year in consideration, or age class

N

Number of the cohort remaining in the population

Nx

Number of remaining in a particular age class (x)

Ix

Survivorship, % of the original cohort to survive

mx

Fecundity

dx

Mortality % of original cohort that dies each year

Net Reproductive Rates

Indicated whrther the populaiton is increasing or deccreasing

- This is true if the emmigration and immigration rates are irrelevant

Survivorship Curve

Y-axis - Log of # of survivors

X-axis - Age

Type I - Arch

Type II - Linear Line

Type III - 1/4 pipe

Life History Tradeoffs

Shaped by natural slection in order to maximixe an organims'ss fitness in the environemnt

High Fecundity

Fast growth rate, sexual maturity at a young age, produce many offspring, lower survirorhsip

Low Fecundity

Slow growth rate, invest in resources in traits that allow them to compete with other individuals, lower fecundity

Population Growth Rate

Change in # of individuals in a population per unit of time while still assuming no immigration or emmigration

Intrinsic Growth Rate

(b-d) = r

r = Per capita rate of Increasing birth rate and death of each indivudal

Rmax

Occurs when conditions are perfect

- b = is at its highest

- d = is at its lowest

Exponential Growth Rate

dN/dt = rN

rN = Rate of population growth

When do you see exponential growth

- Few standing individuals

- Founding population

- Recovering population

dn/dt = rrel N((k-N)/k) = rrel N(1-N/k)

rrel - relative growth rate

k - carrying capacity (is not constant)

Carrying Capacity

1. The point at which the population size is in equilibrium with resources

2. The # of individuals of a species that the environment can support

3. The # of individuals that can survive in the environment

Density Independence

Alter birth and death rates irrespective of population density, usually environmental changes and alters survivorship based on density

Community Ecology

Competition (-/-)

Commensalism (+/0)

Consumption (+/-)

Mutualism (+/+)

Competition

- Individuals interacting where both sustain some cost

- Competition occurs when individuals experience limited resources

- Driving force of natural selection

- Has costs for both species, there is a strong natural selection on both species to avoid the same niche

Intraspecific Competion

Within a species and density dependent

Interspecific Competition

Between species, 2 species with identical niches cannot coexists in that niches indefinitely

Niches

Summary of the environmental factors that influence the growth, survival and reproduction of a species

The when, where and how a species lives its life

N-dimensional niches

n is the number of environmental factors important to the survival and reproduction of the species

Fundamental niche

Physical conditions under which a species might live in the absence of interactions with other species

Realized niche

Actual niches of a species that is restricted through its interaction (like competition) with other species