Interactions of Life
Chapter 24
Living Earth
• The part of Earth that supports life is called
the biosphere.
– Top portion of the crust, all the waters and the
atmosphere that surrounds Earth.
– The biosphere is made up of different
environments that are home to different kinds of
organisms.
• Desert environments vs. tropical environments.
Ecology: the study of interactions that occur
among organisms and their environment
• An ecosystem is all the organisms living in an
area as well as the nonliving parts of that
environment.
– A population is made up of all the organisms in an
ecosystem that belong to the same species.
• All of the grasshoppers in the prairie.
– A community is all the population of all species
living in an ecosystem.
• All of the bison, grasshoppers, birds, etc. in the prairie.
Each organism in an ecosystem needs
a place to live…
• Habitat – the place where
an organism lives.
– In the rainforest, some birds
live inside of dead trees
while salamanders live
beneath fallen leaves and
twigs.
– An organism’s habitat
provides the kinds of food
and shelter, the temperature
and the amount of moisture
the organism needs to
survive.
Biosphere
Ecosystem
Population
Community
Ecology Flow Chart
Biosphere  Ecosystem  Community  Population
1.
2.
3.
4.
5.
Pick an ecosystem (Tropical rainforest, Subtropical savannas, Deserts
and semi-deserts, Oceans, Temperate grasslands, Temperate
forests, Coniferous forests, Alpine and polar regions)
Create an ecology flowchart using irregular shapes.
Start big (at biosphere) and “zoom in” (to population)
Make sure you keep in mind the climate of your ecosystem and all of
the living organisms that would be involved.
Underneath each picture, write a caption so that I know what I’m
looking at and so I know that you know what each level is.
Populations
• Competition: when two or more
organisms seek the same resource
at the same time.
– Competition for food, living space, or
other resources can limit a
population’s size.
– Competition is usually most intense
between members of the same
species.
• why?
• Population size indicates whether a
population is healthy and growing.
• Population density is the size of a
population that occupies a specific
area.
Elements that affect population size…
• Limiting factor: any living or
nonliving feature that restricts the
number of individuals in a
population.
• Carrying capacity: the largest
number of individuals of one
species that an ecosystem can
support.
• Biotic potential: the highest rate
of reproduction under ideal
conditions.
– Pumpkins vs. peaches
• Birth and death rates
• Movement of organisms into or
out of an area.
Interactions within communities
• Producers: organisms that use an
outside energy source (like the sun)
to make energy-rich molecules.
– Plants use photosynthesis
• Consumers: organisms that cannot
make their own energy-rich
molecules and instead obtain energy
by eating other organisms.
– 4 types of consumers
Four types of Consumers
• Herbivores: eat plants
– Deer and rabbits
• Carnivores: eat animals
– Frogs and lions
• Omnivores: eat both plants
and animals
– Pigs and humans
• Decomposers: eat dead
organisms
– Earthworms and bacteria
Food Chain!
• Food chain: a model that shows the feeding
relationships among the organisms in an
ecosystem.
Can’t we all just get along?
• Symbiosis: any close relationship between
species.
– Mutualism: a symbiotic relationship in which both
species benefit.
– Commensalism: a symbiotic relationship in which
one organism benefits and the other is not
affected.
– Parasitism: a symbiotic relationship in which one
organism benefits and the other is harmed.
Can’t we all just get along?
• Niche: an organism’s role in its environment,
including its habitat and food, and how it avoids
danger, finds a mate and cares for its young.
– Predator and Prey!!
• Predator: consumer that captures and eats other consumers.
• Prey: The organism that is captured by the predator.
• Predators limit the size of prey populations, increasing the
number of different species that can live in an ecosystem.
– Cooperative actions improve a species’ survival
• One deer warns others of predators in the area
• Individual ants perform different tasks required for the
survival of all