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Chapter 18
Interactions of Living Things
What is Ecology?
The study of the interactions between organisms and their environment
Interactions between organisms is not simply who eats who but varied, some good some bad
2 parts of ecology
Biotic aspectThe living part of the environmentAnimals, plants, insects, humans
Abiotic aspectThe non-living part of the environmentPhysical factorsRocks, water, soil, light, temperature
Organization in the Environment
OrganismPopulations
Communities
Ecosystems
Biosphere
Single animal
Group of the same animal
Different populations in the same area
Includes the abiotic factors
Earth where life exists
The Energy Connection
All living things need energy to surviveOrganisms are divided into groups
based on how they get energyProducersConsumersScavengersDecomposers
Producers
Make their own food/energyUse the sun to go through the process of photosynthesis
Includes plants, algae and some bacteria
ConsumersCan’t make their own energy, get it by
eating producers or other consumersPrimary consumer – eats the producer Secondary consumer – eats a
consumerHerbivore – eats only plantsCarnivore – eats only animalsOmnivores – eats both plants and animals
Scavenger vs. Decomposer
Scavengers eat dead animals for energyExamples include turkey vultures
Decomposers get energy by breaking down the remains of dead organismsRecyclers, bacteria and fungi
Food Chains and Webs
Food chains represent how energy flows from one organism to the nextRare in nature because animals
usually eat more than one organism
Food webs represent many pathways that energy flows in an ecosystem
Energy Pyramids
Represents the loss of energy by each organism in a food chain or web
Habitat vs. NicheHabitat – the environment in which an
organism livesWhen things like deforestation,
building of roads and buildings occur, habitats are being destroyed
Niche – organisms way of life in the ecosystemIncludes its habitat, food, predators,
competitors and abiotic factors
Niche of the Gray Wolf
ConsumersCarnivores, eating moose, deer,
reindeer, sheep and small animals such as birds and snakes
Social Structure – hunt in packsNurture and teach their youngImportant in population control
Interactions
Most living things produce more offspring than will survive but abiotic and biotic factors will control the population size
Example: frogs
Limiting factors
Populations cannot grow indefinitely because the environment contains only so much food, water, living space and other resources
When one or more becomes scarce, it becomes a limiting factor
Carrying Capacity
The largest population that a given environment can support over a long period of time
When the population gets larger than carrying capacity, limiting factors will cause the population to get smaller
Competition
Can occur among individuals within a population or between populations
Competition for resources, mates, space
Predator and Prey
Prey – the organism that is eatenPredator – the organism doing
the eatingAdaptations
Predator – speed or ambush preyPrey – run away, camouflage,
poisonous, bright colors, groups
Symbiosis
Long term, association between two or more species
3 typesMutualismCommensalismParasitism
Mutualism
Both organisms benefitInsects pollinating flowers
Commensalism
One organism is benefiting and the other is unaffected
Clown fish and sea anemone
Parasitism
One organism is harmed and the other is benefiting
Parasite- benefits
Host - harmed
Coevolution
Long term change that takes place in two species because of their close interactions with each other
Herbivores evolving with the plants they eat
Flowers and their pollinators