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13.1 Ecologists Study Relationships
KEY CONCEPT Ecology is the study of the interactions among living things, and between living things and their environment.
13.1 Ecologists Study Relationships
Ecological research methods include observation, experimentation, and modeling.
• Observation is the act of carefully watching something over time.
• Observations of populations can be done by visual surveys.– Direct surveys for easy to spot
species employ binoculars or scopes.
– Indirect surveys are used for species that are difficult to track and include looking for other signs of their presence.
13.1 Ecologists Study Relationships
• Experiments are performed in the lab or in the field.– Lab experiments give researchers more control. – Lab experiments are not reflective of the complex
interactions in nature.– Field experiments give a
more accurate picture of natural interactions.
– Field experiments may not help determine actual cause and effect.
13.1 Ecologists Study Relationships
• Computer simulations and mathematical models can be used to describe and model nature.
• Modeling allows scientists to learn about organisms or ecosystems in ways that would not be possible in a natural or lab setting.
Ecologists use data transmitted by GPS receivers worn by
elephants to develop computer models of the animal’s
movements.
13.1 Ecologists Study Relationships
OrganismOrganism
• An organism is an individual living thing, such as an alligator.
13.1 Ecologists Study Relationships
OrganismOrganism
Population
Population
• A population is a group of the same species that lives in one area.
13.1 Ecologists Study Relationships
OrganismOrganism
Population
Population
Community
Community
• A community is a group of different species that live together in one area.
13.1 Ecologists Study Relationships
OrganismOrganism
Population
Population
Community
Community
Ecosystem
Ecosystem
• An ecosystem includes all of the organisms as well as the climate, soil, water, rocks and other nonliving things in a given area.
13.1 Ecologists Study Relationships
An ecosystem includes both biotic and abiotic factors.
• Biotic factors are living things.– plants– animals– fungi– bacteria
plants
13.1 Ecologists Study Relationships
• Abiotic factors are nonliving things. – moisture– temperature– wind– sunlight – soil
moisture
sunlight
13.1 Ecologists Study Relationships
OrganismOrganism
Population
Population
Community
Community
Ecosystem
Ecosystem
Biome• A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there.
13.1 Ecologists Study Relationships
A food chain is a model that shows a sequence of feeding relationships.
• A food chain follows the connection between one producer and a single chain of consumers within an ecosystem.
• The base of a food chain is always Producers (plants).• All energy for animals comes from photosynthesis by plants.
DESERT COTTONTAILGRAMA GRASS HARRIS’S HAWK
13.1 Ecologists Study Relationships
• Consumers are not all alike.– Herbivores eat only plants.– Carnivores eat only animals.– Omnivores eat both plants and animals.– Detritivores eat dead organic matter.– Decomposers/scavengers are detritivores that break
down organic matter into simpler compounds.
carnivore decomposer
13.1 Ecologists Study Relationships
• Specialists are consumers that primarily eat one specific organism or a very small number of organisms.
• Generalists are consumers that have a varying diet.
13.1 Ecologists Study Relationships
• Trophic levels are the nourishment levels in a food chain.– Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat
herbivores.– Tertiary consumers are carnivores that eat secondary
consumers.– Omnivores, such as humans that eat both plants and
animals, may be listed at different trophic levels in different food chains.
13.1 Ecologists Study Relationships
A food web shows a complex network of feeding relationships. • An organism may have multiple feeding relationships in an
ecosystem.• A food web emphasizes complicated feeding relationships
and energy flow in an ecosystem.
13.1 Ecologists Study Relationships
energy transferredenergy
lost
An energy pyramid shows the distribution of energy among trophic levels.
• Energy pyramids compare energy used by producers and other organisms on trophic levels.
• Between each tier of an energy pyramid, up to 90 percent of the energy is to heat and waste.
• Only 10 percent of the energy at each tier is transferred from one trophic level to the next.
13.1 Ecologists Study Relationships
Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.
• Biomass is a measure of the total dry mass of organisms in a given area.
tertiaryconsumers
secondaryconsumers
primaryconsumers
producers
75 g/m2
150g/m2
675g/m2
2000g/m2producers 2000g/m2
13.1 Ecologists Study Relationships
• A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem.
tertiaryconsumers
secondaryconsumers
primaryconsumers
producers
5
5000
500,000
5,000,0005,000,000producers
• A vast number of producers are required to support even a few top level consumers.
