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Ecology
AP Biology
Ecology Background Terms
• Population-a group of individuals of the same
species living in the same area
• Community- a group of populations in the same
area
• Ecosystem- the interrelationships between the
organisms in the community and their physical
environment
• Biosphere- all of the ecosystems on earth
• Habitat- a place where an organism lives
• Niche- describes all the biotic (living) and abiotic
(nonliving) resources used by an organism in the
environment- their place in the ecosystem is their
niche
Population Ecology
• The study of the growth, abundance and distribution of
populations. Described by:
• Size of a population- symbolically represented by N- is the
total number of individuals in the population
• Density- the total number of individuals per unit of space
• Dispersion- how individuals in the popuilation are
distributed. They may be clumped (humans in cities),
uniform (trees in an orchard), or random (trees in some
forests)
• Age structure- the abundance of individuals of different ages
• Survivorship curves- describe the mortality (death) of
individuals during different parts of their lifetimes
Age Structure Pyramids
Survivorship Curves
• Type I curves- species in which most individuals
survive to middle age, after that mortality is high. EXhumans
• Type II curves- species in which the length of
survivorship is random- the likelihood of death is the
same at any age. EX- rodents
• Type III curves- species in which most individuals die
young. EX- oysters
Terms Describing Population Growth
• Biotic Potential- maximum growth rate of the
population under ideal conditions
• Carrying capacity- maximum size of the
population in a particular habitat
• Limiting factors- anything that limits the size of
a population. They can be:
– Density dependent- limit the size of a population
based on how close the organisms are to each
other. EX- diseases
– Density independent- limit the size of a population
regardless of how close they live to each other
EX- natural disasters
Population Growth
• Exponential Growthoccurs when a the
reproductive rate is
greater than zero. On a
graph, exponential
growth forms a J-shaped
curve.
• Logistic Growth- occurs
when limiting factors
restrict the size of the
population to the carrying
capacity of the habitat.
On a graph, it forms an
S-shaped curve
Reproductive Strategies
• There are two types:
1. R selected species- exhibit rapid exponential
growth. This type of reproductive strategy is
characterized by opportunistic species- such as
grasses and many insects- that quickly invade a
habitat, quickly reproduce, and then die. They produce
many offspring that are small, mature quickly and
require little (if any) parental care.
2. K selected species- population size remains
relatively constant at the carrying capacity. Species of
this type, such as humans, produce a small number of
relatively large offspring that require extensive
parental care.
r is the growth rate of the population (N), and K is
the carrying capacity of its local environmental
setting. Typically, r-selected species exploit lesscrowded ecological niches, and produce many
offspring, each of which has a relatively low
probability of surviving to adulthood. In contrast,
K-selected species are strong competitors in
crowded niches, and invest more heavily in fewer
offspring, each of which has a relatively high
probability of surviving to adulthood. In the
scientific literature, r-selected species are
occasionally referred to as "opportunistic", while
K-selected species are described as "equilibrium"
Human Population Growth
• A thousand years ago the human population began
undergoing exponential population growth. This was
made possible by:
– Increases in food supply due to domesticating animals
and plants, as well as technological advances in farming
(such as enriching soil with nitrogen)
– Reduction in disease- advances in medicine, such as
antibiotics, vaccines, and proper hygiene
– Water purification and sewage systems- reduce health
hazards
– Expansion of habitat- better housing, warmer clothing,
access to energy for heating/cooling/cooking,
transportation
Human Population Growth
Community Ecology
• Is concerned with the interaction of populations. One
form of interaction is interspecific competition
(between two different species). The following are
ways this competition can be resolved:
– Competitive Exclusion Principle- when two species
compete for exactly the same resource (or occupy the
same niche) one species will eventually outcompete the
other. No two species can occupy the same niche
– Resource partitioning- some species coexist in spite of
apparent competition for the same resources. This is
because they actually pursue slightly different niches. EXfive species of birds coexist in the same type of tree by
feeding on insects in different regions of the tree.
Resource Partitioning
Niches
• Fundamental Niche- the niche an organism occupies in the
absence of competing species
• Realized niche- the actual niche the organism occupies when
competition is present
Cline
• the gradual change in certain
characteristics exhibited by members of a
series of adjacent populations of
organisms of the same species
Competition
• Competition- both species may be harmed
when struggling to gain the same
resources
– Intraspecific- competition within the same
species
– Interspecific- competition between different
species
Predation
• Can be categorized as follows:
– A true predator kills and eats another animal
– A parasite spends most or all of its life living on another
organism (the host)
– A parasitoid is an insect that lays its eggs on a host and the
larvae eat the host when they hatch
– A herbivore is an animal that eats plants. Some may
consume the entire plant.
Predator Prey Relationships
Quick intro:
https://www.youtube.com/watch?v=ZWucOrSOdCs
Research methods (hare):
https://www.youtube.com/watch?v=tOUEgqyGnrw
Symbiotic Relationships
• Symbiosis- when two species live together in close contact.
There are different types:
• Mutualism- both species benefit. EX- acacia trees provide food
and shelter for ants. The ants kills any insects, fungus, or
vegetation on or near the tree
• Commensalism- one species benefits, the other is unaffected
EX- birds nest in trees
• Parasitism- one species benefits, the other is harmed EXtapeworms
3 Symbioses
• https://www.youtube.com/watch?v=Wc
Q5_zaJob0
Competition
• Competition- both species may be
harmed when struggling to gain the
same resources
– Intraspecific- competition within the same
species
– Interspecific- competition between different
species
Coevolution/Defense Mechanisms
• In the contest between predator and prey, some have evolved
unique heritable characterists:
– Secondary compounds- toxic compounds made by plants
that discourage herbivores. EX- tobacco plants
– Camouflage (cryptic coloration)- allows organisms to blend
in EX- leaf and stick bugs
Top 10 weird defenses:
https://www.youtube.com/watch?v=2P7sLWqmK3w
Coevolution/Defense Mechanisms
• Aposematic coloration- is a conspicuous pattern or coloration
that warns predators that they sting, bite, or taste bad
• Mimicry- When two species resemble one another in
appearance. There are two types:
– Mullerian mimicry- where both animals are dangerous.
They share the same appearance- this is thought to teach
predators through power in numbers. EX- wasps and bees
– Batesian mimicry- one species is harmful, but the other is
harmless and gains protection by pretending its
dangerous. EX. Some species of flies/beeltes have yellow
and black markings to resemble bees.
Succession
• Succession- change in species composition in a community
over time. Primary succession occurs when a new habitat
forms- such as with a volcanic island. Secondary
succession occurs after a natural disaster.
• Some of the changes that occur include:
– Pioneer species are the first species to start growing. They
tolerate intense conditions.
– Substrate texture may change from solid rock to sand or to
fertile soil as rock erodes and plant and animal
decomposition occurs
– Soil pH may decrease due to the decomposition of
materials such as leaves
– Soil ability to retain water may change.
– Light availability may change
– Crowding may push out certain species
– The final community structure that forms is called the climax
community
• https://www.youtube.com/watch?v=V49I
ovRSJDs
Energy Flow in Ecosystems
• Trophic Level- a level in a food chain
• Primary producer- autotrophs that convert light
energy into chemical energy. Include plants,
photosynthetic protists, and cyanobacteria
• Primary consumers- herbivores- eat primary
producers
• Secondary consumers- or primary carnivores- eat
the primary consumers
• Tertiary consumers- eat secondary consumers
• Detritovores- consumers that obtain their energy by
eating dead animals and plants (detritus). The
smallest detritovores are called decomposers and
include bacteria and fungus. Others include
earthworms and vultures.
Energy Flow in Ecosystems
• Food chains- a linear
flow of who eats
whom
• Food webs- many
food chains put
together
• As you go up a food
chain- only about
10% of the energy is
passed along- the
other 90% is used by
the organism for
metabolic activities.
• Trophic level- a
level in a food
chain
• Watch the video:
http://www.youtube.com/watch?v=CReZd9
OHEfs and then
• Using the information from the following
website generate a FRQ question or a
Grid-In question about Energy Flow in
Ecosystems
• https://docs.google.com/document/d/1c6O9
5KovdS6mxiwaSuCu2DbfabD4P2fQlF6H4
FNco98/edit?hl=en_US
Biogeochemical Cycle
• Describe the flow of essential elements from the
environment to living things and then back to the
environment.
• We will look at the major storage locations for each
element (reservoirs), the processes through which
each element incorporates into terrestrial plants and
animals (assimilation) and the processes through
which it’s released back into the environment.
Water Cycle
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Reservoirs- oceans, air (as water vapor), groundwater and glaciers.
Evaporation, wind and precipitation move water from oceans to land.
Plants absorb water from the soil.
Animals drink water or eat other organism and use their water.
Water is release from plants through transpiration and from animals when
they sweat. Released from both when they die and decompose.
Carbon Cycle
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Carbon is required for the building of all organic molecules
Reservoirs- atmosphere (as CO2), fossil fuels (coal, oil)
Plants use CO2 for photosynthesis
Animals consume plants and obtain their carbon in organic molecules
Animals breathe out the carbon in CO2
CO2 is released when anything is burned
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Nitrogen is required for making
all amino acids and nucleic
acids
Reservoirs- atmosphere (N2)
and soil
Plants absorb nitrogen as either
NO3 or NH4
Animals obtain nitrogen by
eating plants or other animals
Animals excrete nitrogen is in
their urine
Nitrogen is put into the soil from
the atmosphere (nitrifiation,
nitrogen fixation) and removed
from the soil to the atmosphere
(denitrification)by bacteria
Nitrogen Cycle
Phosphorus Cycle
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Phosphorus is required for the manufacture of ATP and all nucleic acids.
Reservoirs- rocks
Plants absorb phosphorus from soils
Animals obtain phosphorus from eating plants and other animals
Plants and animals release phosphorus when they die and decompose.
• Animals excrete phosphorus is in their urine
Biomes
• Biomes- regions that have common environmental
characteristics
• Tropical rain forests- high temperatures and heavy rainfall.
Tall trees, but little growth on the forest floor due to a lack of
light.
• Savannas- grasslands with scattered trees. Tropical with high
temperatures, but less water than rain forests.
• Temperate grasslands- less water and lower temperatures
than savannas.
• Temperate deciduous forests- warm summers and cold
winters where trees drop their leaves.
• Deserts- hot and dry. Animals and plants have adaptations to
deal with harsh conditions.
Biomes
• Taigas- coniferous forests. Cold winters and
precipitation in the form of snow.
• Tundras- winters so cold the ground freezes. During
the summer, the upper topsoil thaws, but the deeper
soil (called permafrost) stays frozen.
• Fresh water biomes- ponds, lakes, streams, rivers
• Marine biomes- estuaries (where rivers meet
oceans), and the ocean
Biomes
Biome video
• https://www.youtube.com/watch?v=v7c
Z3b6PH2s
• During the video take notes on the
major characteristics of each biome on
your study guide.
Human Impact on Biosphere
• Human activity damages the
environment:
– Greenhouse effect- the
burning of fossil fuels
increases carbon dioxide
in the atmosphere. The
increased carbon dioxide
causes more heat to be
trapped near the earth’s
atmosphere. As a result,
global temperatures are
rising. This could raise
sea levels by melting
more ice.
– http://climate.nasa.gov/ca
uses
Human Impacts
• Ozone depletion- the ozone
layer form in the upper
atmosphere when UV
radiation make O2 form O3
molecules (ozone). The
ozone absorbs UV radiation
and prevents it from reaching
earth where it can damage
the DNA of plants and
animals. Pollutants such as
CFCs (chlorofluorocarbons)
have been used as
refrigerants and propellents
and remove O3 from the
atmosphere. This has left
major areas of thinning
called ozone holes.
Human Impacts
• Acid rain- burning fossil fuels and other industrial
pollutants contain sulfur dioxide and nitrogen
dioxide. When they react with water they produce
sulfuric acid and nitric acid. They return to the soil
in rain or snow and can kill plants and animals.
• Desertification- Overgrazing of grasslands that
border deserts transform grasslands into desert.
• Deforestation- Clear cutting of forests causes
erosion, flooding, and changes in weather patterns.
The slash and burn method of clearing tropical
rainforests for agriculture increases atmospheric
carbon dioxide, contributing to the greenhouse
effect. Because most of the nutrients in rainforests
are stored in the plants, the soil is poor and can
only support agriculture for a few years.
Human Impacts
• Biological Magnification- some
pollutants, such as the
pesticide DDT or mercury, are
not broken down in the
environment and accumulate in
the fatty tissues of organisms.
As you go up in a food chain
the concentration of these
pollutants is higher. The
biological magnification of DDT
led to several species of birds,
including the bald eagle, nearly
going extinct.
Human Impacts
• Algal Blooms- can be caused by fertilizer or sewage running off into a lake.
When the algae eventually die, bacteria break them down, and the
bacterial growth depletes oxygen in the lake. The result is oxygen
starvation for many animals, including fish and invertebrates. This is called
eutrophication.
• Reduction in species diversity- as a result of human activities- including
habitat destruction, and hunting/poaching