Chapter 2 Notes, Ecology
What is Ecology?
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Ecology is the branch of biology that studies
the relationships between organisms, their
habitats, and all the living and nonliving factors
involved in those habitats.
Some of the topics that ecologists seek to
understand and study are...
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Adaptations and physiological responses
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The cycles and movement of energy and matter
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Ecological succession and population dynamics
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The biosphere, biomes and communities
What is the Biosphere?
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The biosphere is the portion of the Earth that
includes life.
Since life is found almost everywhere on the surface
of Earth, you might say the entire surface of the
earth is the biosphere.
More specifically, the biosphere is made up of living
factors, which we call biotic factors, and nonliving
factors which we call abiotic factors.
Biotic and Abiotic Factors
Levels of Organization in Ecology
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Starting with a simple organism and working our
way up to the biosphere, we can see increasing
levels of organization in ecology.
A group of similar organisms make up a
population.
All of the populations of organisms in the same
habitat make up a biological community.
A biological community, plus the abiotic factors
involved in that community make up an
ecosystem.
Levels of Organization in Ecology
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A group of
ecosystems that are
found in the same
climate or region
make up a biome.
All the biomes of the
world make up the
biosphere.
Ecosystem Interactions
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In a biological community, every organism
has a specific area where it lives. This area
varies in size and shape depending on the
organism and it is called its habitat.
For an insect a habitat may be a tree.
For a lynx, wolf, bear, or wolverine a habitat
may be several hundred square miles.
Each organism plays a specific role in its
habitat. This role is called its niche.
Community Interactions
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Organisms living in the same biological
communities interact in different ways.
When more than one organism uses a resource in
a biological community, competition occurs.
Competition can occur for food, shelter, water,
nutrients, space, sunlight, soil, habitat etc.
Another interaction that occurs in a biological
community is predation.
A close relationship that exists when two or more
species live together is called symbiosis.
Predator-Prey Relationships
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The relationship between predators and prey
have been studied in great detail on moose and
wolves on Isle Royale National Park.
Populations of lynx and hare have also been
studied in detail.
Isle Royale is on an island so it is a closed
system. So it is an ideal location to study the
link between large predators and their prey.
Hare populations fluctuate in 10 year cycles.
Lynx populations follow the hares.
Predator-Prey Relationships
Predator-Prey Relationships
Symbiotic Relationships
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There are three different types of symbiotic
relationships
Mutualism is when two or more organisms live
closely together and they each benefit from each
other in the relationship.
Commensalism is when two or more organisms
live closely together and one organism benefits
from the other but the other organism is neither
helped nor harmed.
Symbiotic Relationships
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Parasitism is when one organism benefits at the
expense of another organism.
Parasites can be either endoparasitic, like
roundworms, tapeworms, flukes, and bacteria, or
they can be ectoparasitic like fleas and ticks.
Another type of parasitism is called brood
parasitism. An example of this is the brownheaded cowbird which lays its eggs in other birds'
nests. The birds then hatch and often push the
other birds out of the nest.
Mutualism
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One of the best examples of mutualism is
insect pollination in plants. The plant benefits
by cross-pollination of its flowers. The insect
benefits by obtaining food from pollen.
Commensalism
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A remoras fish attached to a shark would be
an example of commensalism. The remoras
receives a free ride and free meal from the
scraps that the shark doesn't eat. The
remoras neither help nor harm the shark.
Parasitism
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Head lice, mosquitos, and dog heartworms are
all examples of parasites
Flow of Energy in an Ecosystem
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Ecologists also study the flow of energy in
ecosystems.
Organisms that collect energy from either the
sun or inorganic substances like hydrogen
sulfide are called autotrophs.
Organisms that get their energy from eating
other organisms are called heterotrophs.
Heterotrophs that eat plants are called
herbivores. Heterotrophs that eat other
heterotrophs are called carnivores.
Flow of Energy in an Ecosystem
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Organisms that eat
both plants and
animals are called
omnivores.
Organisms that eat
dead or decaying
organic matter are
called detritivores.
Models of Energy Flow
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Ecologists use models to show the flow of energy
through an ecosystem.
Food chains are simple models that show the
flow of energy through an ecosystem.
Food webs are models that show the many
interconnected food chains and metabolic
pathways in which energy flows through a
community. More realistic model.
Each step or change in a level of a food chain or
food web is called a trophic level.
Food Chains and Webs
Food Webs
Ecological Pyramids
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Another model ecologists use to show the relative
amount of energy and biomass at each trophic level is
called an ecological pyramid.
Biomass is the total mass of living matter.
It has been estimated that for every increase in a
trophic level on an ecological pyramid, there is an
estimated 90% decrease in energy.
Biomass at each trophic level decreases as well.
The relative number of species found at each trophic
level decreases as well.
Ecological Pyramid
Cycles in the Biosphere
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If mass, energy, and matter flowed in only one
direction, eventually all the available mass,
energy, and matter would be used up.
Fortunately, mass, energy, and matter travel
through cycles that make them available again to
living organisms that depend on them.
Essential nutrients that are crucial to all living
organisms must be recycled as well.
These cycles that living organisms depend on are
called biogeochemical cycles.
The Water Cycle
The Carbon and Oxygen Cycles
The Nitrogen Cycle
The Phosphorus Cycle