Interactions of Living Things

7th Grade Science

PART 1

Biotic vs. Abiotic

-Biotic – all LIVING parts of environment.-ex: tree, fly, people

-Abiotic – all NONLIVING parts of environment.-ex: water, soil, sunlight, temp.

Levels of Environmental Organization

1. Organism2. Population – all same species that live in area3. Community – all species that live in area4. Ecosystem – community plus abiotic factors5. Biosphere – all ecosystems, anywhere life

exists

Salt Marsh – page 6

-What are some biotic factors in this marsh?*cordgrass *jellyfish*egret *heron*algae *marsh crab

-What are some abiotic factors?*water *sunlight*soil *temperature

PART 2

LIVING THINGS NEED ENERGY

Players in the Energy Game

-Producers – use sunlight to make food-ex: plants, algae

-Consumers – eat other organisms-herbivore – eats only plants-omnivore – eats both plants & animals-carnivore – eats only animals-scavenger – eats dead plants & animals

-Decomposers – get energy by breaking down dead organisms

-ex: bacteria & fungi-called nature’s recyclers

Food Chains

-Diagram that shows energy flow from one organism to another

-Why are these rare in nature?

Food Webs-More realistic than chains

-Interconnected chains show feeding relationships in ecosystem

-Arrows – is eaten by

Energy Pyramids

-diagram that shows loss of energy as it passes through food chains

Amount of energydecreasesas youmove upthe levels

Amount oftoxinsincreaseas youmove upthe levels

PART 3

TYPES OF INTERACTIONS

Limiting Factors

-Scarce resource that limits size population can grow

-ex: food becomes a limiting factor when population outgrows amount of

food available

Carrying Capacity

-Largest population an environment can support at any given time

-When a population grows larger than carrying capacity, limiting factors cause individuals to die or leave

Competition

-2 or more individuals or populations trying to use the same resource.

Predators vs. Prey

-Predator – organism that eats the prey-wide variety of methods & abilities for getting food

A cheetah’s speed gives it an advantage over other predators competing for the same prey

Prey Adaptations

-Prey have methods to keep from being eaten:1. stay in groups2. camouflage3. defense (poison, chemical, physical)4. burrowing

Stay in groups or Herds

Camouflage

22

Defense

23

Warning Coloration

24

Symbiosis

-Close, long-term association between members of 2 or more species

-classified as one of the following:1. mutualism2. commensalism3. parasitism

25

Mutualism

-Both organisms benefit from the interaction.-ex: you & e.coli in your stomach!!!

26

Commensalism

-One organism benefits, the other is unaffected.-ex: sharks & remoras

27

Parasitism

-One organism benefits, the other is harmed.-organism that benefits - parasite-organism harmed - host

-ex: Caterpillar & Wasp eggs