IV. How do Organisms Interact
A. Carrying capacity
1. Carrying capacity= The
number of organisms that can
live in an area
2. Limiting factors= factors that
set the amount of organisms
that can live in an area
–
–
–
–
–
Food
Water
Shelter
Space
mates
https://youtu.be/QI2ixJeIxEU?list=PLe4Jn7ZzDg8R9m
What are limiting
factors in the tundra?
What are limiting
factors in the desert?
C. Competition
https://youtu.be/H9MV5CgPgIQ https://youtu.be/wNqiclBUxdY
1. Organisms compete for
resources
–
–
–
–
Food
Water
Space
Shelter
2. Can compete against their
own species or another
species
3. Plants also compete
resources
https://youtu.be/4EU_tJWXaKc
–
–
Larger roots can absorb more
water
Growing high allows for more
direct sunlight
D. Symbiosis= long term relationship between different
species living together
https://youtu.be/zSmL2F1t81Q
1. Parasitism (+/-): symbiotic relationship in which one
organism benefits and one is harmed
–
–
Mosquito bite sucking your blood
Fleas or ticks on a dog
2. Mutualism (+/+): symbiotic relationship in which BOTH
organism benefit
– Bacteria in your gut helps you to digest food and the bacteria get a
meal and shelter
– Nile Crocodile with the Egyptian Plover bird (Crocodile bird)- bird
gets food & protection and the croc gets teeth cleaned of parasites
– Clown fish and the sea anemone
– Lichen is made of a fungus and plant-like algae: one gives shelter
and the other provides food
3. Commensalism (+/0): symbiotic relationship in which one
organism is helped and the other is not harmed or
helped
– Egret bird “hitches” a ride with the buffalo
II. How energy moves through the ecosystem
https://youtu.be/MuKs9o1s8h8
1. Food web: energy moves through an ecosystem through
food chains, energy chains, or food webs
2. All food chains start with the sun for energy
3. Levels of the food chain/web:
https://youtu.be/cMZKgvWTvkg
a. Producers: Plants, protists & microorganisms use the suns
energy through photosynthesis to make sugars (glucose)
b. Consumers: cannot make their own food
• Herbivores: plants eaters
• Carnivores: meat eaters
• Omnivores: eat both plants and meat
• Decomposer: eat waste or dead organisms
4. Arrows show the flow of energy through the food from
one level to another
–
–
“mouth” opens up to eat the food
Rabbit eats the grass or energy from the grass moves into the
rabbit
https://youtu.be/Zhycg7gHz38
Food chain vs food web
1. Food chain is simple showing only once “choice” or level
2. Food webs show multiple choices or levels representing
what may truly happen in nature
3. Both get the initial energy from the sun
4. Both have producers at the first level
5. A food web consists of multiple food chains
Energy Pyramids
1. Energy pyramid= diagram that shows the amounts of energy
that flow through each level of a food chain
2. Producers have the greatest amount of energy
3. Top predators have the least amount of energy
4. Energy is passed from the bottom to the top & stored I the net
organisms body
5. Some energy is lost as heat
Heat
Heat
Heat
Heat