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Ecology
Obj. 3a & e
Ecosystems
 An ecosystem is all the organisms that live
in an area together with the nonliving
factors of the environment
 Ex. Pond or pine forest
 Ecology is the study of how organisms
interact with each other & the physical
environment
Populations
• All the organisms in an ecosystem that
belong to the same species
– Ex. Mice living in a meadow or pine trees
in a forest
• Species are a group of organisms that
can mate to produce offspring that can
produce more offspring
– Ex. Brown pelican or human
Community
• All the populations of different
species that live in an ecosystem &
share resources
– Ex. Pine tree forest forms a community
with populations of deer, mice, raccoons,
bacteria, mushrooms, & ferns
– Ex. An arctic community might include
populations of fish, seals that eat fish, and
polar bears that hunt and eat seals
Limiting Factors that affect
populations
• Food: plants make their own food, but other
organisms obtain food by eating other
organisms
• Water: required by all living things to move
materials around cells & tissues in the body
• Light: required by plants & other organisms to
make food through photosynthesis
• Living Space: organisms need room to obtain
resources & reproduce
Ex. Polar Bear Habitat
The polar bears main habitat is
offshore pack ice, along coasts and islands
of the Arctic region. Polar bears prefer
the ice packs to other parts of their
habitat because it allows them to remain
in close contact with their main food
source, the seal.
Niche
• The unique ways an organism survives,
obtains food & shelter, reproduces, cares
for its young, and avoids danger
– Homeostasis: an organisms ability to keep
the proper internal conditions no matter
what is going on outside the organism’s
body
• Example of niche: A male lion’s mane attracts a
mate
• Why does each species have its own niche?
Ex. Polar Bear Niche
• Large feet and short, sharp, stocky claws are
adaptations to this environment.
• Thick layer of fat under a thick fur to provide
protection from extreme cold temperatures
• Polar bears depend on sea ice as a platform
for hunting seals.
• Eat seals, walrus, & fish
• Care for young for 2 years
Interactions Within Communities
• All organisms need ENERGY to
survive.
• The sun is the source of energy
that fuels most life on Earth
Feeding Relationships
• 3 main groups
– Producers
– Consumers
– Decomposers
Producers:
Autotrophs
• Organisms that make their own food
using energy from the sun & raw
materials from the environment
– Most producers are plants that contain
chlorophyll required for photosynthesis
Photosynthesis
• Plants use carbon dioxide and hydrogen from
light-energy in the presence of chlorophyll to
make glucose and oxygen
– Directly or indirectly produces food for almost all
organisms
– Removes carbon dioxide from and adds oxygen to
the atmosphere
– Phytoplankton & algae also play a huge role as
producers in the environment
CO2 + H2O + sunlight
(energy)
oxygen + Glucose
(sugar)
Respiration
• Respiration is a chemical reaction that
occurs in the mitochondria of cells
– combines oxygen & food to release energy
for living organisms, carbon dioxide as a
waste product, and water
– Both plants and animals use aerobic
respiration
– Opposite of photosynthesis
Oxygen + Glucose
(sugar)
CO2 + H2O + energy
Consumers:
Heterotrophs
• Organisms that cannot make their own
food & Obtain energy by eating other
organisms
• Three Types:
– Herbivores: eat only plants/producers
– Carnivores: eat only animals
– Omnivores: eat both plant & animals
Decomposers:
Heterotrophs
• Organisms that feed on the dead remains or
waste products of other organisms to obtain
energy
• Help recycle once-living matter by breaking it
down into simpler substances to be used as food,
nutrients absorbed by plant, or consumed by
other organisms
– Ex. Bacteria, earthworms, & fungi
Food Chains
• A model that shows the
flow of energy through
feeding relationships
among organisms in a
particular ecosystems
Food Webs
• A model that links the organisms within
an ecosystem by how they depend on
each other for food.
• The lines drawn represent the flow of
energy through the ecosystem & show a
variety of food chains
Food Web
Relationships b/t Populations
• 3 main categories of relationships
– Competition
– Predation
– Symbiosis
Competition
• Occurs when more that one individual
or population tries to make use of the
same limited resources
– Ex. Food, water, or space
Predation
• Type of feeding relationship in which
one animal captures & eats another
animal for food
– Animal being eaten is the prey
– Animal doing the eating is the predator
– Predator/prey relationships help keep an
ecosystem in balance by preventing any
one population from growing too large
Symbiotic Relationships
• Symbiosis: any close relationships
between organisms
– Mutualism: both species benefit
• Ex. A hummingbird drinks the nectar
from a petunia and carries the
flower’s pollen to other flowers
Symbiotic Relationships
• Commensalisms: one organism
benefits while the other organism is
unharmed
–Ex. A heron lives near a herd of
cattle eating the insects the cattle
stir up as they pass through the
grass
Symbiotic Relationships
• Parasitism: one organism called a parasite
feeds on the cells, tissue, or fluids of
another organism called a host
– Parasites benefits while the host is usually
weakened but not killed
– Ex. A flee lives on and drinks the blood of a
dog