Ecology General Concepts
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1) Ecology is the study of the relationship between living things and their environment -where they live.
Scientists who study ecology are called ecologists.
2) An ecosystem is the environment where one or more organisms live. An ecosystem includes everything
that affects and interacts with the organism and has two main parts:
biotic factors - all the living things (plants, animals, fungi, bacteria, etc.) in the environment.
abiotic factors- all the natural resources or physical nonliving things in the environment including
light, air, water, temperature, rocks, sticks, dirt, etc.
3) The world environment is organized into different levels going from small to large. The first level
contains just the individual organism. The second level contains many similar organisms called a
population. The third level contains many different populations which forms a community. The fourth
level contains communities combined with their abiotic environment to form an ecosystem. Large groups
of ecosystems that share similar climate and precipitations are called biomes. Finally, all the ecosystems
and biomes in the whole planet earth combine to form the biosphere.
4) A habitat is the specific place or ecosystem where a type of organism lives its whole life. It provides all
the biotic and abiotic resources necessary for the individual organism to survive. The size of an organism’s
habit depends on its needs. Two or more organisms may share the same habitat if their needs overlap.
Examples of habitats are: ants - anthill; deer - deciduous forest; humpback whale - open ocean; mite - the
ear of moth. Habitats are specific to the individual organism population and the individual place.
5) A niche is the job or activities that an organism does to survive in its habitat. It includes many things
such as: the organism’s role in the food chain (is it a producer, consumer, herbivore, omnivore, etc.?), how
it protects itself (run, fight, camouflage, etc.), how it makes shelter (caves, burrows, dens, nest, etc.), how it
gets food (grazes, catches, scavenges, etc.), how it nurtures its young, social behaviors (runs in packs, sings,
mates for life, pecking orders, etc.).
6) Although different organisms may live together in the same habitat or ecosystem, different organisms
cannot have the same niche in that ecosystem. Organisms have adapted for their niche by having
specialized body parts. For example, special beaks, claws, fur, teeth, colorations, glands, leaves, size, etc.
all help the organism do its specialized role in the ecosystem.
7) A population is a group of organisms of the same type living together in the same place. Individuals in
the population compete with one another for food, shelter, and mates.
8) The carrying capacity of an environment is the largest population that can be supported over a long
period of time. Populations cannot grow indefinitely because the environment contains only so much food,
water, living space, and other natural resources. If a natural resource (abiotic factor) becomes scarce,
populations decrease.
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9) Factors that control the size of populations are called limiting factors. They include: availability of
natural resources; space; disease; safety from predators; natural disasters such as storms and wild fires;
relationships or interactions with other species; etc. Humans also become limiting factors to many species
through hunting, urban construction, farming, industrialization, deforestation, pollution - air and water, fires,
etc.
10) Overpopulation is a limiting factor that occurs when the flow of energy though various food webs has
been upset or unbalanced. The overpopulation of a species usually has negative consequences for the
environment. Natural resources are often depleted at a rate faster than they can be replenished. As a result,
the habitat and niche of other species changes sometimes to the point where the population cannot survive
and becomes extinct.
11) Alien or exotic species are species that are released into an environment that they had not previously
existed. They are limiting factors to the environment because they upset the food chains in the area and
compete for natural resources. Since exotic species are free from the predators in their native habitat, they
often overpopulate destroying other species. Alien species include zebra muscles, purple loosestrife (wild
flower), kudzu vines, Indian mongoose, brown tree snake.
12) A community is a group of all the populations of different species that live in an ecosystem. For
example, in a pond ecosystem the community consists of the frog population, dragonfly population, algae
population, largemouth bass population, cattail population, etc.
13) Ecological succession is the gradual process by which a community in a particular place develops,
grows, and replaces another community. There are two types of succession.
14) Primary succession occurs when a community starts to grow in an area that previously did not contain
soil and living organisms. Fires, volcanoes, storms, rising and dropping sea levels, and glaciers may expose
a new area. For example, a glacier retreats leaving exposed rocks. The rocks chemically and mechanically
weather providing nutrients for the first species to live in the new area called the pioneer species. Lichens
are a symbiotic combination of fungi and algae that are able to extract nutrients from bear rocks, and are
often the pioneer species for primary succession. Dirt is formed over a long period of time providing
nutrients for grasses and eventually trees. As more and more plants start growing, animals move in.
15) Secondary succession begins on preexisting soil. An existing community is disturbed and the area
gradually returns to its previous condition. Farming, natural disasters, or alien species might destroy
communities. Pioneer species such as plant seeds then develop the soil. Eventually, over time as more and
more species grow in the new environment, a mature ecosystem or climax community develops. Climax
communities have great biodiversity so they are more resistant to limiting factors.
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16) The term biodiversity means variety of life. It refers to the many different kinds of living things found
in a particular place. The greater number of different things that live in an area, the greater the biodiversity.
Destroying habitats reduces biodiversity and reduces the overall health of the biosphere. Humans can help
increase biodiversity by reducing pollution, reducing constructions and fuel consumption, recycling,
planting trees, etc.
17) Scientists have identified and classified over 26 million different living things (biotic factors) on Earth
and put them into categories according to (a) what they look like, (b) cell organization, (c) chemical makeup, (d) the way they grow and respond to their environment, (e) and their assumed and uncertain ancestral
relationship (how they evolved). The science of classifying living things is called taxonomy.
18) The largest category of living things is called a kingdom. Everything that is considered to be a alive
can be placed into one of six kingdoms.
(I) archaebacteria: most primitive form of bacteria, may not have a cell wall
(II) eubacteria: simple single cell organisms with no nucleus, may be a producer or consumer
(III) protists: complex single celled organisms with distinct internal parts (organelles); or simple
multi-celled algae, protozoans, or slime molds
(IV) fungi: simple to complex organism that reproduce by spores and obtain food by decomposing
substances
(V) plants: complex multicellular organisms that use photosynthesis to make their own food
(VI) animals: complex multicellular organisms that feed on other organisms and are able to move on
their own
19) Each kingdom is broken down into smaller categories which get broken into more categories. The more
broken down a category gets, the fewer types of organisms within that category, but the organisms will have
more in common. The categories go from largest to smallest in this order.
Kingdom
Phylum
Class
Order
Family
Genus
Species - Breed
20) Bacteria are simple cells with no real nucleus. They are found everywhere in the world in all
temperatures and environments. They have three basic shapes which are round (cocci), rod-shaped (bacilli),
and spiral (spirilla). There are two whole kingdoms of bacteria because of their genetic diversity.
21) Protists are mostly single celled microscopic organisms except for algae. There are three major phyla
of protists: algae (plant-like protists), protozoans (animal-like protists), and slime molds (fungi-like
protists).
22) Fungi are divided into four main groups based upon its shape and the way it reproduces. Threadlike
fungi include all molds. Club fungi include umbrella shaped mushrooms, toadstools, and puffballs. Sac
fungi is the largest group of fungi. It included yeasts, mildews, truffles, and the edible morels. Imperfect
fungi include all other types of fungi such as athlete’s foot and penicillin.
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23) Currently there have been more than 263,000 identified species of plants in the biosphere. The
kingdom of plants is usually broken into two major phyla - the bryophytes or nonvascular plants, and the
tracheophytes or vascular plants.
24) Nonvascular plants have no roots or leaves. They have no way of transporting water throughout the
organism so they are small. They rely totally on osmosis (water going directly into each cell). Mosses and
liverworts are the most common examples.
25) Vascular plants have roots and leaves. They are able transport water and nutrients throughout the
whole plant, so they can be any size.
26) There have been more than 248,000 identified kinds of vascular plants, many more than nonvascular
plants. Vascular plants are broken into two main classes - plants that produces seeds and plants that do not.
Plants that do not produce seeds include ferns and horsetails. Plants that do produce seeds are broken into
two orders - gymnosperms and angiosperms.
27) Gymnosperms produce seeds in cones. They do not have flowers. Common examples are evergreen
trees and bushes and conifers.
28) Angiosperms include all flowering plants that produce seeds inside a fruit. There are more than
235,000 species of angiosperms.
29) Scientists have named over 1,000,000 species of animals. These are divided into two super-phyla
which are the chordates and invertebrates. About 97% or two dozen phyla of all animals fit into the
invertebrate super-phylum. There is only three phyla of chordates. Most all chordates are vertebrates - have
a backbone.
30) Animals in the invertebrate phyla have no backbone. They are classified mainly by their basic body
plans or types of symmetry.
31) Invertebrates with radial symmetry have their parts arranged in a circle around a central point. For
example, if you were to draw an imaginary line across the top of a sea anemone, you would see that both
halves look the same. But you could draw the line in any direction and still see two similar halves.
32) An animal with bilateral symmetry has a body with two similar halves. For example, if you draw a
line down the middle of an ant, you see the same features on each side of the line. Some animals such as
sponges have body parts that are arranged with no symmetry at all. Their body plan is asymmetrical.
33) Major invertebrate phyla include: Porifera (sponges), Cnidaria (jelly fishes, corals, sea anemones),
Annelida (segmented worms), Mollusk (snails, clams, oysters, octopuses, squids), Arthropod (crustaceans
- crabs, lobsters; centipedes; spiders; insects), Echinoderm (starfishes, sea urchins, sea lilies)
STOP! Well Done! You are ready to take Pre-test A
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34) All chordate animals have a hollow nerve cord that is filled with fluid. With vertebrates, this is called a
spinal cord. The vertebrate phyla is broken into seven major classes. Five of the classes are cold-blooded
or ectotherms (body temperature changes with their surroundings), and two of the classes, birds and
mammals, are warm-blooded or endotherms (maintain a constant body temperature). The classes are as
follows: (I) jawless fishes - sea hags, sea lampreys (II) cartilaginous fishes - sharks, sting rays (III) bony
fishes - catfish, bass, tuna, eels (IV) amphibians - frogs, toads, salamanders (V) reptiles - turtles, snakes,
lizards, alligators (VI) birds - hawks, sparrows, penguins, ostriches (VII) mammals - mice, elephants,
whales, monkeys
35) In an ecosystem living organisms or biotic factors are also grouped by how they get food for energy.
There are three main groups that each have different roles - producers (autotrophs), consumers
(heterotrophs), and decomposers. Each group depends on each other and could not survive if one group
were removed.
36) Producers, also called autotrophs, are organisms that make their own food by a chemical process
called photosynthesis. Most producers are green plants. However a few bacteria, protists, and fungi are
also producers.
37) Producers have special organelles (miniature organs) in each cell called chloroplasts that contain
molecules called pigments. These pigments absorb energy from the sun. Chlorophyll is the main pigment
that gives plants their green color. Photosynthesis is the chemical process by which producers capture light
energy from the sun and use it to combine water with air to form sugar or food. The chemical equation is:
6CO2 + 6H2O + light energy
carbon plus water
dioxide
plus
sunlight
C6H12O6 + 6O2
yields
sugar
(food)
and
oxygen
38) The food that producers make supplies them with energy and also becomes a source of energy for the
organisms that eat the producers. Without plants, the primary producers, consumers and decomposers
would not be able to live. Producers always start every food chain.
39) A consumer, also called a heterotroph, is an organism that cannot make its own food. It must eat
producers or other organisms for energy. All animals are consumers. A few protists and a very few exotic
plants are also consumers.
40) Consumers make food through a process called respiration. Oxygen and sugar are combined to
produce carbon dioxide water and energy. Consumers breathe in the oxygen that is produced by the
photosynthesizers. The oxygen is used to break down the food to release energy that powers all life
processes. The breakdown of food also produces carbon dioxide which is removed from the body when we
exhale. The chemical equation is:
C6H12O6 + 6O2
6CO2 + 6H2O + energy
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41) There are many kinds of consumers: (I) herbivore - eats only plants; includes cows, zebras, horses,
deer, some insects (II) carnivores - eats only other consumers (meat); includes cats, owls, seals, spiders,
seals, hawks (III) omnivore - eats both plants and animals; includes raccoons, monkeys, bears, skunks,
turtles (IV) scavengers - animals that feed on the bodies of dead animals; includes vultures, hyenas, worms
42) Decomposers are organisms that get energy by decaying or breaking down chemically the remains of
dead organisms. They are nature’s recyclers. Most bacteria and fungi and some protists are decomposers.
When an organism dies, decomposers decay the body extracting the last bit of energy from it. The common
left over materials such as water, carbon dioxide, and minerals can then be reused by producers to make
sugar through photosynthesis. Decomposers are a special type of heterotroph that eat at the cellular level.
43) Decomposers are also important because of their role in the nitrogen cycle. The nitrogen cycle is the
movement of nitrogen from the environment into living organisms and back into the environment. Nitrogen
makes up about 78% of the earth’s atmosphere. It is necessary for all living organisms because it is the
primary building block in proteins and DNA.
44) The nitrogen in the air cannot be used by producers and consumers. It must be fixed or converted by
bacteria in the ground into a useable form for plants called nitrates. Some plants called legumes (beans and
clover) actually have bacteria in their roots. Once the plants use the nitrates, consumers eat the plants so the
nitrogen is transferred. The consumers die and give off wastes transferring the nitrates back to the
environment. Other bacteria unfix the nitrates, or change it back into nitrogen returning it into the air. The
cycle then starts over again.
45) The carbon released by consumers and decomposers is essential to all living organisms because it is part
of all biological molecules. The carbon cycle is the movement of carbon from the environment into living
things and back into the environment. Carbon dioxide is removed from the air and used by producers
during photosynthesis. Most consumers get the carbon they need from eating the producers. Carbon is
released back into the environment in three ways: during the respiration of consumers; during
decomposition; and during combustion - the burning of coal, oil, natural gas, and other fossil fuels.
46) In general, the flow of energy or cycle of energy in an ecosystem starts with sunlight (the ultimate
source of all energy on Earth) which is absorbed by the producers, goes to the consumers, then to the
decomposers, and back to the producers to start all over again. For example, plants make food through
photosynthesis. The plants may then eaten by consumers. After the consumer dies, it is recycled by the
decomposers. The nutrients made by the decomposer are used by the producers again.
47) Food chains show how the flow of energy in an environment moves from one organism to the next.
Organisms get eaten by the organism the arrow is pointing to. For example an animal goes into the mouth
of another animal. Food webs are interconnected food chains. They show how food chains are related.
Food chains and webs always start with producers!
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48) As energy flows from producers to consumers to decomposers, some is lost at each feeding level in the
chain because most of the energy is either used by the organism or is given off as heat. The loss of energy
at each level can be represented by an energy pyramid. The energy pyramid has a large base and becomes
smaller at the top. At the base or the first level are the producers. The energy and the number of organisms
are very high. At the second level are the various consumers. For each level or feeding stage the energy
and number of organisms decreases so the pyramid becomes smaller at the top. Herbivores are sometimes
called primary consumers. They are in the second level of the pyramid. Carnivores are sometimes called
secondary consumers, and are in the third level. Omnivores are sometimes called tertiary consumers, and
are at the top of the food pyramid because they eat everything. Technically, scavengers and decomposers
are not part of the energy food chain/web or pyramid because they do not kill and eat thereby transferring
energy from one organism to another. Sometimes they are shown at the top of the pyramid or at the end of
the web.
49) In a community the different populations depend on each other for food, shelter, and other natural
resources. Often individual organisms of different populations interact with each other forming five
distinct interactions or relationships. These relationships are limiting factors that control a population’s
size. The relationships can be broken into two categories - predation and symbiosis.
50) Predation relationships involve the struggle for both biotic and abiotic factors among populations in an
ecosystem. These include:
(I) predator/prey: organisms called predators eat organism called prey. For example, a hawk will
prey
upon a mouse.
(II) competition: animals of the same species fight for food, space, or the right to mate. For example,
two bucks locking horns, a pack of wolves fighting over a carcass, a bear marking its territory.
51) Symbiosis is a close long-term association between two or more species where at least one individual is
benefitted. There are three types of symbiosis.
(III) mutualism: a relationship in which all organisms are benefitted. For example, bees pollinate
flowers - the bees gather pollen for honey, and the flowers can make seeds; bacteria live inside your
intestine - the bacteria help you digest food and give you vitamins while the bacteria are given food.
(IV) commensalism: a relationship in which one organism is benefitted and the other is unaffected. For
example, a bird builds a nest in a tree - the bird has a place high off the ground, but the tree gains nothing.
(V) parasitism: a relationship on which one organism is benefitted while the other organism is harmed.
The organism benefitting is the parasite. The organism being hurt is the host. Most parasites do not kill
their hosts so that they can continue feeding. For example, leeches, fleas, ticks, and lice all live on the
host and eat its blood without killing it.
52) A biome is a large group of ecosystems that share similar climates, rain fall, soil types, and organisms.
There are seven major land biomes and two major water biomes in the biosphere.
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53) The desert biome has less than 10 inches of rainfall each year. Average temperatures are 100°F in the
summer and 45°F in the winter. Soil is very poor, so producers are scattered. Plants include cacti and wildflowers. Most animals are nocturnal and include snakes, lizards, small rodents, bats, and foxes.
54) The tundra biome gets 12-20 inches of rainfall each year. Average temperatures are 54°F in the
summer and -14°F in the winter. The weather is perpetually cold and windy. Soil is poor and allows only
for shallow rooted plants to grow such as mosses, grasses, and small shrubs. Permafrost is the soil below
the surface. It stays frozen year round. Tundra animals include polar bears and caribou. There are two
types of tundra. Arctic tundra is near the poles, and alpine tundra is above the tree line of tall mountains.
55) Grassland biomes are found between forests and deserts and are generally flat. There are two types of
grasslands. The temperate grassland biome gets 10-30 inches of rainfall each year. Average temperatures
are 86°F in the summer and 32°F in the winter. Soil is rich and good for many plants. Animals include
prairie dogs, mice, and large grazing animals such as bison.
56) The savanna grassland biome gets 59 inches of rainfall each year. Average temperatures are 93°F in
the summer and 61°F in the winter. It is a tropical grassland with scattered clumps of trees. The savannas
of Africa are inhabited by some of the most diverse groups of large herbivores in the world such as zebras,
giraffes, and elephants.
57) There are three types of forest biomes -Coniferous (taiga), temperate deciduous, and tropical rain.
58) The coniferous forest biome also called the taiga gets 14-30 inches of rainfall each year. Average
temperatures are 57°F in the summer and 14°F in the winter. Coniferous forests do not change much year
round. They are found in areas with long cold winters and short cool summers. Areas consist mainly of
thick forests of cone bearing evergreen trees. Animals include squirrels, bears, mountain lions, and moose.
59) The temperate deciduous forest biome gets 30-49 inches of rainfall each year. Average temperatures
are 83°F in the summer and 43°F in the winter. These forests lose their leaves every Fall season. They
support a variety of animal life.
60) The tropical rain forest biome contains more species than any other biome on the planet. It gets up to
160 inches of rainfall each year. There are no seasons here. Average temperatures are 93°F in the day and
68°F at night. The top soil is very thin and poor for growing. Many plants and animals live up in the tree
tops or canopy.
61) The largest biome in the world is the marine biome. It based on salt water
and contains all oceans and seas. Plankton lives in the marine biome. It produces
the majority of oxygen in the atmosphere and is the
most abundant form of life in the world.
62) The freshwater biome is the smallest biome in the world. Factors that limit
species growth include water quality issues.
Good Job! You are
finished. Read the
microscope pages 15 16 and skim over
pages 17 - 19. Then
you are ready to take
Pretest B!