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