Ecology Part 4. Populations Part 5. Communities Part 6.
Biodiversity and Conservation
Slide 2
Population Characteristics 1.Population Density: The number of
organisms per unit area 2.Spatial Distribution: Dispersion: The
pattern of spacing a population within an area 3 main types of
dispersion Clumped Uniform Random The primary cause of dispersion
is resource availability Population Ecology: Population
Characteristics
Slide 3
Population Limiting Factors 3.Population growth rate How fast a
given population grows Factors that influence this are: Natality
(____ rate) Mortality (_____ rate) Emigration (the number of
individuals moving _________ a population) Immigration (the number
of individuals _________ a population) Population Ecology:
Population Characteristics birth death away from moving to
Slide 4
Population Limiting Factors Density-independent factors Factors
that limit population size, regardless of population density. These
are usually abiotic factors They include natural phenomena, such as
weather events Drought, flooding, extreme heat or cold, tornadoes,
hurricanes, fires, etc. Population Ecology: Density-independent
factors
Slide 5
Population Limiting Factors Density-dependent factors Any
factor in the environment that depends on the number of members in
a population per unit area Usually biotic factors These include
Predation Disease Parasites Competition Population Ecology:
Density-dependent factors
Slide 6
Understanding Exponentials Put your pens down for a minute
& think about this: An employer offers you two equal jobs for
one hour each day for fourteen days. The first pays $10 an hour.
The second pays only 1 cent a day, but the rate doubles each day.
Which job will you accept? Population Ecology: Population Growth
Rate
Slide 7
Understanding Exponentials Population Ecology: Population
Growth Rate Job 2 lags for a long time before exponential growth
kicks in! Now, how much would your employer owe you if you stayed
at this job for another 2 weeks? What would happen if this type of
growth took place within a population?
Slide 8
What population do you think this is? Population Ecology:
Population Growth Rate What letter does this curve resemble?
Slide 9
The USCB estimates that the world population exceeded 7 billion
on March 12, 2012
Slide 10
Population growth models Exponential growth model Also called
geometric growth or J-shaped growth. First growth phase is slow and
called the lag phase Second growth phase is rapid and called the
exponential growth phase Bacteria can grow at this rate, so why
arent we up to our ears in bacterial cells?
Slide 11
Population growth models Limits to exponential growth
Population Density (the number of individuals per unit of land area
or water volume) increases as well Competition follows as nutrients
and resources are used up The limit to population size that a
particular environment can support is called carrying capacity (k)
Population Limiting Factors
Slide 12
So, what do you think is going to happen to the human
population? We will probably reach our carrying capacity. Our
growth rate will start to look like most organisms, which is the
Logistic Growth Model Carrying Capacity (k) What letter does this
curve kind of look like? http://en.wikipedia.org/
wiki/Overpopulation
Slide 13
Population growth models Logistic Growth Model Often called the
S-shaped growth curve Occurs when a populations growth slows or
stops following exponential growth. Growth stops at the populations
carrying capacity Populations stop increasing when: Birth rate is
less than death rate (Birth rate < Death rate) Emigration
exceeds Immigration (Emigration > Immigration) Population
Limiting Factors
Slide 14
Population growth models Logistic Growth Model The S-curve is
not as pretty as the image looks 1.Carrying capacity can be raised
or lowered. How? Example 1: Artificial fertilizers have raised k
Example 2: Decreased habitat can lower k 2.Populations dont reach k
as smoothly as in the logistic graph. Boom-and-Bust Cycles
Predator-Prey Cycles Population Ecology: Population Growth
Models
Slide 15
Slide 16
Species that follow this pattern usually 1.Have a Boom-and-Bust
Life Cycle 2.Have short life spans 3.Produce many offspring
4.Smaller organisms i.e., fruit flies, mice, locusts, oysters
5.Dont maintain a population near carrying capacity 6.Controlled by
density-independent factors They are called r-strategists (for rate
of increase) Population Limiting Factors Population Ecology:
Reproductive Strategies
Slide 17
Species that follow this pattern usually 1.Have long life spans
2.Produce few offspring that have a better chance of living to a
reproductive age 3.Are larger organisms i.e., elephants, whales,
humans 4.Maintain a population at or near k 5.Controlled by
density- dependent factors They are called k- strategists (for
karrying kapacity) Population Limiting Factors Population Ecology:
Reproductive Strategies plateau K
Slide 18
r and K strategists A logistic equation can describe the
self-limiting growth of a biological population. where r is the
maximum growth rate of the population (N), and K is the carrying
capacity of its local environmental setting, d stands for
derivative, and t for time.growth ratepopulationcarrying
capacityderivativetime In r/K selection theory, selective pressures
drive evolution in one of two generalized directions: r- or
K-selection
Slide 19
Traits that are thought to be characteristic of r-selection
include: high fecundity small body size early maturity onset short
generation time ability to disperse offspring widely Traits that
are thought to be characteristic of K-selection include: large body
size long life expectancy production of fewer offspring extensive
parental care until they mature r and K strategists Evolved to take
advantage in unstable environment, density independent Evolved to
take advantage in stable environment, density dependent
interactions
Slide 20
Communities Review: A community is a group of interacting
populations that occupy the same area at the same time. Community
Ecology: Communities
Slide 21
Communities Limiting Factors Any abiotic or biotic factor that
restricts the numbers, reproduction, or distribution of organisms.
Community Ecology: Communities Name some
Slide 22
Communities Range of Tolerance The limits within which an
organism can exist. Community Ecology: Communities Think: Effects
of global warming/climate change?
Slide 23
Ecological Succession The change in an ecosystem that happens
when one community replaces another as a result of changing biotic
and abiotic factors Community Ecology: Ecological Succession
Slide 24
Ecological Succession Consists of 2 types: Primary Succession
Secondary Succession Community Ecology: Ecological Succession
Slide 25
Ecological Succession Ecological Succession: Primary The
establishment of a community in an area of exposed rock that does
not have topsoil is called Primary Succession. It occurs very
slowly at first Community Ecology: Ecological Succession: Primary
Succession
Slide 26
Ecological Succession: Primary The first organisms to arrive
are usually lichens or mosses, which are called pioneer species.
They secrete acids that can break down rock Their dead, decaying
organic materials, along with bits of sediment from the rock make
up soil. Community Ecology: Ecological Succession: Primary
Succession
Slide 27
Ecological Succession Ecological Succession: Primary Small
weedy plants and other organisms become established; dispersal As
these organisms die, additional soil is created Community Ecology:
Ecological Succession: Primary Succession
Slide 28
Ecological Succession Ecological Succession: Primary Seeds
brought in by animals, water and wind begin to grow in the soil.
Eventually enough soil is present for shrubs and trees to grow.
Community Ecology: Ecological Succession: Primary Succession
Slide 29
Ecological Succession Ecological Succession: Primary The
stable, mature community that eventually develops from bare rock is
called a climax community. Community Ecology: Ecological
Succession: Primary Succession
Slide 30
Ecological Succession Community Ecology: Ecological Succession:
Secondary Succession Ecological Succession: Secondary Disturbances
(fire, flood, windstorms) can disrupt a community. After a
disturbance, new species of plants and animals might occupy the
habitat.
Slide 31
Ecological Succession Community Ecology: Ecological Succession:
Secondary Succession Ecological Succession: Secondary Pioneer
species in secondary succession are usually plants that begin to
grow in the disturbed area. This is much faster than primary
succession
Slide 32
Ecological Succession Community Ecology: Ecological Succession
Ecological Succession: End point? Cannot be predicted Different
rates of growth & human involvement make it impossible to know
if a true climax community has been reached.
Slide 33
What would happen if all of the jackrabbits in a food web died
suddenly? Is the disappearance of one species from Earth important,
or will another species fill its niche? Biodiversity and
Conservation: Introduction
Slide 34
Keystone species is a species that has a disproportionately
large effect on its environment relative to its abundance. Play a
critical role in maintaining the structure of an ecological
community Affect many other organisms in an ecosystem Examples: 1)
Pacific Coast: purple sea urchin can damage kelp forests by chewing
through kelp holdfasts The sea otter is an important predator of
sea urchins. 2) Grey wolves in Yellowstone 3) Can you think of any
other examples?
Slide 35
Biodiversity What is Biodiversity? The variety of life in an
area that is determined by the number of different species in that
area. There are 2 main types: Biodiversity and Conservation: What
is biodiversity? Genetic DiversitySpecies Diversity
Slide 36
Biodiversity Biodiversity and Conservation: Why is biodiversity
important? Teosinte: A distant relative of corn Domestic corn plant
Penicillin: Derived from bread mold Madagascar Periwinkle: Used to
treat childhood forms of leukemia
Slide 37
Extinction Rates The gradual process of becoming extinct is
known as background extinction. Mass extinctions: When a large
percentage of all living species become extinct in a relatively
short period of time. Ex: 250 MYA: Over 90% of species died
Biodiversity and Conservation: Extinctions
Slide 38
Estimated number of Extinctions since 1600 Biodiversity and
Conservation: Extinctions GroupMain- land
IslandOceanTotalApproximate Number of Species Percent of Group
Extinct Mammals305148540002.1 Birds2192011390001.3
Reptiles12002163000.3 Amphibians200242000.05 Fish22102319,1000.1
Invertebrates49481981,000,000+0.01 Flowering Plants
2451390384250,0000.2
Slide 39
Five Most Recent Mass Extinctions Biodiversity and
Conservation: Extinctions Ordovician Period (444 MYA) Devonian
Period (360 MYA) Permian Period (250 MYA) Triassic Period (200 MYA)
Cretaceous Period (65 MYA)
Slide 40
Activity: Understanding Geological Time Working in your groups,
you will get the following supplies: A meter stick A roll of 5
meters of paper Colored pencils Using the worksheet, plot out the
dates. 1 million years is a millimeter 1 billion years is a
meter
