The Levels of Organization That Ecologists Study Are

The Levels of Organization That Ecologists Study Are

Chapter 3 Notes


Section 3-1

Ecology is the study of interactions among organisms and between organisms and their environment.

The levels of organization that Ecologists study are:

Species (individual)-a group of organisms so similar to one another that they can breed and produce fertile offspring

Population-Groups of individual that belong to the same species and live in the same area.

Communities- Groupings of different populations that live together in a specific area.

Ecosystems-A collection of all the organisms that live in a particular place together with their nonliving, or physical, environment.

Biome-A group of ecosystems that have the same climate and similar dominant communities.

***The highest level of organization that ecologists study is the entire biosphere itself.

A group of mice and a group of rabbits DO NOT make up the same population because they ARE NOT the same species.

The methods used to study ecology are:




Section 3-2

The main source of energy for life processes is sunlight (chemical energy).

Autotrophs (plants) are self feeding (aka producers), they use chemical energy (sunlight) to make their own food = PHOTOSYNTHESIS

We are all consumers.

HERBIVORES: an organism that only eats plants

CARNIVORES: an organism that eats meat

OMNIVORE: an organism that eats both animals and plants

DETITRIVORES (mites, worms, snails): Feed on plant and animal remains or other dead matter.

DECOMPOSERS (bacteria and fungi): Break down organic matter.

**Organic in science means it containscarbon.

FOOD CHAIN: a series of steps in which organisms transfer energy by eating and being eaten. Food chains show that energy flows through an ecosystem in ONE direction, from the sun or inorganic compounds to AUTOTROPHS (aka producers) and then to various HETEROTROPHS (aka consumers). (See page 69 in text)

Each step in a food chain is call a trophic level (primary or 1st level, secondary or 2nd level, tertiary or 3rd level and so on…)

FOOD WEBS are many food chains linked together (see page 71 in text)

Energy Pyramid-Shows the relative amount of energy available at each trophic level

Biomass Pyramid: Biomass pyramids are shaped that way to show that biomass is largest at the base, and decreasing in amount as it goes through the top. The two types of biomass pyramids are the upright and the inverted. The upright pyramid (see below) is found in most ecosystems. It results when the combined weight of producers is larger than the combined weight of consumers. An inverted type results when the combined weight of producers is smaller than the combined weight of consumers.

Biomass means the total mass of all living material in a specific area, habitat, or region.

Pyramid of numbers: The pyramid of numbers shows the relationship in terms of the number of producers, herbivores and the carnivores at their successive trophic levels. There is a decrease in the number of individuals from the lower to the higher trophic levels. The number pyramid varies from ecosystem to ecosystem.

Pyramid of Number