Download Trophic Levels Food Chains , Webs and Pyramids

Intro to Ecology
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Ecology- the study of interactions between organisms and their environments, focuses on energy transfer
• It is a science of relationships.
The environment is made up of two factors:
• Biotic factors- all living organisms inhabiting the Earth
• Abiotic factors- nonliving parts of the environment (i.e. temperature, soil, light, moisture, air currents)
Levels of organization in Ecology:
1. Organism- any cellular form exhibiting all of the characteristics of
life, an individual. (The lowest level of organization in an ecosystem)
2. Population- a group of organisms of one species living in the same
place at the same time that interbreed and compete with each
other for resources
3. Community- all the populations in a common environment that are
interdependent.
4. Ecosystem- populations in a community + abiotic factors they
interact with
5. Biome- life supporting portions of Earth composed of ecosystems (temperate forests, marine).
6. Biosphere-Earth
ALL ECOSYSTEMS HAVE HABITATS AND NICHES
 Niche - the role a species plays in a community (job)
 Habitat- the place in which an organism lives out its life (address)
A niche is determined by the tolerance limitations of an organism, or a limiting factor.
Limiting factor- any biotic or abiotic factor that restricts the existence of organisms in a specific
environment. (Amount of water, food or temperature)
It’s All About Relationships
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Feeding Relationships
1. Producer- Consumer
Producer- all autotrophs (plants), they trap energy from the sun
• Bottom of the food chain
Consumer- all heterotrophs: they ingest food containing the sun’s energy
• Herbivores- eat only plants- fruit, bark, seeds, pollen, roots etc. Herbivores are prey animals
• Carnivores- eat meat. Carnivores are predators OR scavengers
• Omnivores- eat plants and animals
• Decomposers- break down organisms- return nutrients to the soil
2. Predator- Prey
Predator- hunts to kill and eat
Prey-is hunted and eaten
3. Parasite- Host
Parasite- harms the host and moves from host to host
Host-provides a home and is harmed
Symbiotic Relationships (species living together)
1. Commensalism- One species benefits and the other is neither
harmed nor helped
a. polar bears and cyanobacteria
2. Parasitism- One species benefits (parasite) and the other is harmed
(host) Parasite-Host relationship
a. Tick and a dog
3. Mutualism- beneficial to both species
a. Cleaning birds on cows
Trophic Levels
Food Chains , Webs and Pyramids
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Each link in a food chain, web or pyramid is known as a trophic level.
• Represent a feeding step in the transfer of energy and matter in an ecosystem
Food chain- simple model that shows how matter and energy move through an ecosystem
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Food web- shows all possible feeding relationships in a community at each trophic level
Represents a network of interconnected food chains
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Biomass- the amount of organic matter comprising a group of
organisms in a habitat.
• As you move up a food chain, both available energy and
biomass decrease.
• Energy is transferred upwards but is less with each transfer.
• Represented with a Food Pyramid
Toxins in food chainsWhile energy decreases as it moves up the food chain, toxins increase in potency.
This is called biological magnification
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Nutrient Cycles
Cycling maintains homeostasis (balance) in the environment.
1. Water cycle
a. Evaporation
b. Transpiration
c. Condensation
d. Precipitation
2. Carbon cycle- Photosynthesis and respiration cycle carbon and oxygen
through the environment.
a. PHOTOSYNTHESIS and CELLULAR RESPIRATION:
i. Returns carbon to the soil
ii. Plants absorb it then release it
iii. Animals consume it then release it
iv. Dead things decompose and release carbon
v. Humans burn things and release carbon
3. Nitrogen cycle (Atmospheric nitrogen (N2) makes up 78-80% of air- Organisms can’t use it in that form)
a. Lightning and bacteria convert nitrogen into usable forms.
b. Only in certain bacteria (and industrial technologies) can fix nitrogen nitrogen fixation.
c. Nitrogen fixation-converts atmospheric nitrogen (N2) into ammonium (NH4+) which can be used
to make organic compounds like amino acids.
d. Nitrogen Fixing Bacteria
e. Some live in a symbiotic relationship with plants of the legume family (e.g., soybeans, clover,
peanuts).
f. Some live free in the soil.
g. Nitrogen-fixing cyanobacteria are essential to maintaining the fertility of semi-aquatic
environments like rice paddies.
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