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ECOLOGY 2nd part

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Dia Shannon

on 14 October 2016

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Transcript of ECOLOGY 2nd part

ECOLOGY
An introduction to ecology and the biosphere
Human impact on ecosystems and the biosphere
ecosystems
Community ecology
population ecology
The scientific study of interactions between organisms and their environments.
Why is
biodiversity
important?
Discover why a high diversity of species sustains ecosystems, which in turn provide important services to humans.
The
biodiversity
crisis
Why is
biodiversity
threatened
?
Population
Dynamics
Organism
Population
Community
Ecosystem
Biome
Biosphere
Where Are We?
Ecology is the study of organism interactions with each other and the environment.

Ecological processes occur at multiple levels of organization on Earth.

Each level of organization emerges from the processes of the level below it
Big Questions:
Make Sure You Can
How Populations Grow
Theory
Reality
Human Population Growth
All members of a species in a contiguous area.

Populations are dynamic.
Organisms enter a population in 2 ways:
Birth
Immigration
Organisms leave a population in 2 ways:
Death
Emigration
Model 1: Exponential Growth
Model 2: Logistic Growth
The growth of a population continues indefinitely.
Assumes no resource limitation.

Can be described by:

change in number of individuals (
dN
)
change in time (
dt
)

(
r
): the "
per capita rate of increase
", how many offspring per individual in the population
As long as (r) is a positive value, a population will continue to increase at an exponential rate.

Higher (r) values will lead to faster rates of increase.

if (r) is 0, the population will not increase or decrease.

if (r) is negative, the population will decrease.
The growth of a population decreases as the population approaches the "
carrying capacity
" (
K
) of the environment.

Models resource limitations.

The effect of (K) on (r) becomes greater as (N) approaches (K)
How are real populations structured?
How do real populations grow?
How does evolution effect
life history traits
?
How does the environment affect population growth?
Measuring Population Size
Population Distribution
Population Demographics
It can be difficult to estimate population size accurately.

"
Mark-Recapture
": 1 common method
Capture and mark members of the population.
Release them.
Recapture members of the population.

Number of marked individuals

Total population size
Individuals tend to be distributed in three major patterns:
Clumped
Uniform
Random
Demographics: The study of a population's vital statistics and how they change over time.
Demographic Data can be arranged in tables (e.g.
life tables
,
reproductive tables
), or graphs (e.g.
survivorship curves
).
There are 3 major types of
survivorship curves
demonstrated in real populations:
Exponential Growth
Typically occurs in small populations, well below the carrying capacity of the environment.
Logistic Growth
Much more common. Typically populations oscillate around the carrying capacity.
Life History Traits
:
Any trait that affects an organism's life table.
Costs and benefits of all adaptations.
Reproductive strategies
Parental Care
Semelparity:
Produce a lot of offspring, once.
Iteroparity:
Produce a few offspring, repeatedly
Number of babies varies inversely with amount of parental care
R-Selected vs. K-Selected
Selection for traits that maximize reproductive success at low-population densities
Selection for traits that maximize reproductive success at high population densities
The effect of population density on population growth
Density Dependent Population Regulation
Competition
Predation
Territoriality
Waste
Accumulation
Intrinsic Factors
Disease
The underlying root of all
anthropogenic
ecological problems
Historical Human Growth Rate
The human population has been in a period of accelerated exponential growth since the industrial revolution...

...that growth rate is slowing
The decrease in growth rate is not uniform across the globe.
As countries industrialize, various changes in demographics occur (the "
demographic transition
")
It is, as of yet, unclear what the global carrying capacity for the human population is.
How are populations structured?

How are populations affected by the environment?
Explain how populations can be mathematically modeled.

Describe the relationships among all terms in population models.

Compare ideal populations to real-world populations.

Explain patterns of life-history, distribution, and survivorship.

Explain the costs and benefits of particular life-history characteristic adaptations and strategies.

Describe historical and current trends in the human population.
A comparison of the exponential and logistic growth models for a population
N = ~1,100
The Agave Plant: Semelparous
Elephants (and all mammals): Iteroparous
Data showing parental survivorship as a function of brood size in kestrels.
"Age-Structure Pyramids"
Human Population Growth
Recaptured marked individuals

Total recaptured individuals
=
Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing.
an age-specific summary of the survival pattern of a population
(or fertility schedule) is an age-specific summary of the reproductive rates in a population
a plot of the proportion or numbers in a cohort still alive at each age
low death rates during early and middle life, then drops steeply as death rates increase among alder age-groups (e.g. humans, large mammals those produce relatively few offspring but provide them with good care)
very high death rates for the young, but then flattens out at death rates decline for those few individuals that have survived to a certain critical age (organisms that produce very large numbers of offspring but provide little or no care, e.g. fishes, oysters, marine invertebrates)
constant rate over the life span (e.g. some annual plants, various invertebrates such as
Hydra
, some lizard species, and some rodents such as gray squirrel)
(from Latin semel, once, and parito, to beget)
(from the Latin itero, to repeat)
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