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ECOLOGY 2nd part
Transcript of ECOLOGY 2nd part
An introduction to ecology and the biosphere
Human impact on ecosystems and the biosphere
The scientific study of interactions between organisms and their environments.
Discover why a high diversity of species sustains ecosystems, which in turn provide important services to humans.
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
Make Sure You Can
How Populations Grow
Human Population Growth
All members of a species in a contiguous area.
Populations are dynamic.
Organisms enter a population in 2 ways:
Organisms leave a population in 2 ways:
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 (
change in time (
): 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 "
) 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
It can be difficult to estimate population size accurately.
": 1 common method
Capture and mark members of the population.
Recapture members of the population.
Number of marked individuals
Total population size
Individuals tend to be distributed in three major patterns:
Demographics: The study of a population's vital statistics and how they change over time.
Demographic Data can be arranged in tables (e.g.
), or graphs (e.g.
There are 3 major types of
demonstrated in real populations:
Typically occurs in small populations, well below the carrying capacity of the environment.
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.
Produce a lot of offspring, once.
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
The underlying root of all
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 "
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.
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
, some lizard species, and some rodents such as gray squirrel)
(from Latin semel, once, and parito, to beget)
(from the Latin itero, to repeat)