Ecology is the study of interactions between organisms and their environment. The biosphere is the global ecosystem, encompassing all living things found in air, land, and water on Earth. Ecologists study how both biotic factors (living things) and abiotic factors (non-living things) influence organisms and populations within various levels of organization, from individuals to ecosystems. Energy and matter flow through ecosystems via food chains and food webs, with only about 10% of available energy being transferred between trophic levels. Key biogeochemical cycles such as the water, carbon, nitrogen, and phosphorus cycles recycle critical elements and compounds.

1. What is Ecology?
• The branch of biology that developed from
natural history is called ecology.
• Ecology is the study of interactions that take
place between organisms and their
environment.
• Ecologists may ask what a coyote eats, how day
length influences plants or migrating birds, or
why tiny shrimp help rid ocean fishes of
parasites.

2. The Biosphere
• On earth, living things are found in the air, on
land, and in both fresh and salt water.
• The biosphere is the portion of Earth that
supports living things.
• Range of the biosphere is from high in the
atmosphere to the bottom of the oceans.
• The biosphere supports a diverse group of
organisms in a wide range of climates.

3. • The climate, soils, plants, and animals in one
part of the world can be very different from
those same factors in other parts of the world.
• Living things are affected by both the physical
or nonliving environment and by other living
things.
• Factors that affect organism are both abiotic
and biotic.

4. Abiotic Factors
• Examples of abiotic factors include air
currents, temperature, moisture.
• Ecology includes the study of features of the
environment that are not living because these
features are part of an organism’s life.
• Abiotic factors have obvious effects on living
things and often determine which species
survive in a particular environment.

5. Biotic Factors
• Living things affect other living things.
• All organisms depend on others directly or
indirectly for food, shelter, reproduction, or
protection.
• Examples plants, animals, bacteria, any thing
that is living.

6. Levels of Organization
• To help ecologists understand the interactions
of biotic and abiotic parts of the world, they
have organized the living world into levels.
• 1. Organism- an individual living thing that is
made of cells, uses energy, reproduces,
responds, grows and develops.
• 2. Population- A group of organisms, all of one
species, which interbreed and live in the same
place at the same time.

7. • 3. Biological community- all the populations of
different species that live in the same place at
the same time.
• 4. Ecosystem- populations of plants and
animals that interact with each other in a
given area and with the abiotic components of
that area.
• 5. Biosphere- the portion of earth that
supports life.

8. Interactions within populations
• Organisms in a population share the resources
of their environment may determine how far
apart the organisms live and how large the
populations become.
• Compete with each other for food, water,
mates, or other resources.
• Competition increases when resources are in
short supply.

9. Interactions within communities
• A change in one population in a community
may cause changes in the other populations.
• Changes can be minor like an increase in
predators cause a decrease in prey.
• Changes can be major like a population may
use up the resources and in turn affecting
another population.

10. Biotic and abiotic factors form
ecosystems
• Biotic factors like insects, grass, trees, squirrels
and abiotic factors like water, temperature
make an ecosystem.
• Two major kinds of ecosystems-terrestrial
ecosystems (forest, meadows, etc.)and
aquatic ecosystem (salt water and fresh water)

11. Organisms in ecosystems
• The place where an organism lives out it’s life
is a habitat.
• Ecosystems covers a large area of the earth.
Habitat covers a small area of an ecosystem.
• Habitat size varies from organism to organism.
• Habitats are also shared with different species
of organism.

12. Survival Relationships
• A predator is a type of consumer like a lion or
an insect-eating bird.
• The animals predators eat are called prey.
• Predator-prey relationships such as the one
between cats and mice involve a fight for
survival.
• But not organisms living in the same
environment are in a continuous battle for
survival.

13. • Studies have shown that most species survive
because of the relationships they have with
other species.
• The relationship in which there is a close and
permanent association between organisms of
different species is called symbiosis.
• Symbiosis means living together.

14. The three kinds of symbiotic
relationships
• 1. Mutualism
• Two species of organisms benefit from living
in close association.
• Ex. Ants and acacia trees living in the
subtropical regions of world. The ants protect
the acacia tree by attacking any animal that
tries to feed on the tree. The tree provides
nectar and a home for ants.

15. • 2. Commensalism
• One species benefits and the other species is
neither harmed nor benefited.
• Ex. Spanish moss on the branches of trees.
The moss benefits because it uses the tree for
support. It holds on to the tree. The tree does
not benefit but is not getting harmed either.

16. • 3. Parasitism
• One organism benefits while harming another.
• Ex. Ticks or fleas on animals. The ticks or fleas
gets nutrients from animal.
• Parasites have evolved in such a way that they
harm, but usually do not kill the host species.
• If host dies then parasite dies also if they don’t
find another host.
• Other examples of parasites: certain bacteria,
tapeworms, roundworms, mistletoe.

17. Nutrition and Energy Flow
Ecologists trace the flow of energy through
communities to discover nutritional
relationships between organisms.
The producers: Autotrophs
The ultimate source of the energy for life is
the sun. Plants use the sun’s energy to
manufacture food in a process called
photosynthesis.

18. Grass and trees are autotrophs. Some unicellular
organisms such as green algae, also make their
own nutrients.
Other organisms in the biosphere depend on
autotrophs for nutrients and energy. These
dependent organisms are called consumers.

19. The consumers: Heterotrophs
A bison eats grass, a deer nibbles the leaves of a
clover plant and owl swallows a mouse.
The bison, deer and owl are consumers,
incapable of producing their own food. They
obtain nutrients by eating other organisms.
Heterotrophs include organisms that feed on
only autotrophs, feed on only other
heterotrophs, or feed on both autotrophs and
heterotrophs.

20. Types of heterotrophs
1. Herbivore – a heterotroph that feeds only on
plants. Ex. Rabbits, grasshoppers, squirrels,
bees.
2. Heterotrophs that eat other heterotrophs.
1.Carnivores- animals that kill and eat only
other animals. Ex. Lions,
2. Scavenger- do not kill for food but eat
animals that have already died. Ex. Black
vultures.

21. 3. Omnivores- consume both autotrophs and
heterotrophs (plants and meat). Ex. Raccons,
opossums and bears.
Decomposers – organisms that break down
dead and decaying plants and animals into
simpler molecules that can be more easily
absorbed. Ex. protazoans, many bacteria, and
most fungi.

22. Flow of matter and energy in
ecosystems
When you eat food, such as an apple you
consume matter.
Matter, in the form of carbon, nitrogen, and
other elements, flow through the levels of an
ecosystem from producers to consumers.
The apple also contains energy from sunlight
that was trapped in the plant during the process
of photosynthesis .

23. As you cycle the matter of the apple, some
trapped energy is transferred from one level to
the next. At each level, a certain amount of
energy is also transferred to the environment as
heat.
Question
How do matter and energy flow through
ecosystems?

24. Food chains: Pathways for matter and
energy
A food chain is a simple model that scientist use
to show how matter and energy move through
an ecosystem.
In a food chain, nutrients and energy move from
autotrophs to heterotrophs and, eventually, to
decomposers.

25. A food chain is drawn using arrows to indicate
the direction in which energy is transferred from
one organism to the next.
Ex. Berries  mice  black bear
Most food chains consist of two, three, four
transfers. The amount of energy remaining in
the final transfer is only a portion of what was
available at the first transfer. A portion of the
energy is given off as heat at each transfer.

26. Trophic levels represent links
in the chain
Each organism in a food chain represents a
feeding step, or trophic level, in the passage of
energy and materials.
A first order heterotroph is an organism that
feeds on plants, such as a grasshopper.
A second order heterotroph is an organism that
feeds on the first order heterotroph. Ex. Bird
that feeds on a grasshopper.

27. A food chain represents only one possible route
for the transfer of matter and energy through
and ecosystem.
Many other routes may exist. Many different
kinds of organisms eat a variety of foods, so a
single species may feed at several trophic levels

28. The Food Web
Ecologists interested in energy flow in an
ecosystem may set up experiments with as
many organisms in the community as they can.
Food web shows all the possible feeding
relationships at each trophic level in a
community.
Food web represents a network of
interconnected food chains formed by
herbivores and carnivores.

30. Energy and trophic levels: Ecological
Pyramids
• An ecological pyramid can show how energy
flows through an ecosystem.
• The base of the ecological pyramid represents
the autotrophs, or first trophic level.
• Higher trophic levels are layered on top of one
another

32. The pyramid of energy illustrates that the
amount of available energy decreases at each
succeeding trophic level.
The total energy transfer from one trophic level
to the next is only about ten percent because
organisms fail to capture and eat all the food
energy available at eh trophic level below them.

34. Cycles In Nature
Since energy is also transferred to the
environment as heat generated by the body
processes of organisms.
Sunlight is the primary source of all this energy,
and is always being replenished by the sun.
Matter, in the form of nutrients, also moves
through, or is part of, all organisms at each
trophic level. But matter is cycled and is not
replenished like the energy from sunlight.

35. • There is a finite amount of matter.
The atoms of carbon, nitrogen, and other
elements that make up the bodies of organisms
alive today are the same atoms that have been
on Earth since life began.
Matter is constantly recycled. It is never lost.

36. The water cycle
Life on earth depends on water.
1. Evaporation- water evaporates from lakes and
oceans and becomes water vapor in the air.
2. Transpiration- the loss of water through the
leaves of plants.
Where do the drops of water that form on a cold
can of soda come from?

37. The water vapor in the air condenses on the
surface of the can because the can is colder than
the surrounding air.
3. Condensation- water vapor condenses. Forms
clouds.
4. Precipitation- rain, ice, or snow
Animals breathe out water vapor when they
breath. When they perspire or urinate, water
also is returned to the environment.

39. The carbon cycle
All life on Earth is based on carbon molecules.
Atoms of carbon form the framework for
proteins, carbohydrates, fats, and other
important molecules.
Carbon is the molecule of life.

40. During photosynthesis, energy from the sun is
used by autotrophic organisms to convert
carbon dioxide gas into energy-rich carbon
molecules that many organisms use for food and
a source of energy.
Plants take in carbon in the form of carbon
dioxide for growth and energy.

41. Heterotrophs, which feed either directly or
indirectly on the autotrophs, use these carbon
molecules for growth and energy.
Carbon is taken out of the atmosphere by
photosynthesis.
Carbon is put back in the atmosphere by
respiration, fuel combustion, and open burning

43. The nitrogen cycle
When you add nitrogen fertilizer to a lawn,
houseplants, or garden, you may see that they
become greener, bushier, and taller.
Even though the air is 78% nitrogen, plants seem
to do better when they receive nitrogen
fertilizer.

44. This is because most plants cannot use the
nitrogen in the air. They use nitrogen in the soil
that has been converted into more usable
forms.
Certain bacteria convert the nitrogen from air
into these more usable forms. Chemical
fertilizers also give plants nitrogen in a form they
can use.

45. The cycle:
1. Nitrogen fixing bacteria convert nitrogen in a
form that plants can use.
2.Plants use nitrogen to make molecules such
protein.
3. Herbivores eat plants and convert plant’s
protein into an animal protein.
4. Then carnivores eat herbivores and convert
the protein in a form that they require.

46. 5. Urine, contains nitrogen compounds so
animal put nitrogen back to the water or soil.
6. Organism die and decay, nitrogen returns to
the soil and eventually to the atmosphere or
plants can reuse the nitrogen.
7. Soil bacteria also act on these molecules and
put nitrogen back into the air.

48. The Phosphorus Cycle
All organisms require phosphorus for growth
and development. Phosphorus cycles in two
ways.
Short term cycle.
1. Plants obtain Phosphorus from the soil.
2. Animals obtain phosphorus by eating plants.
3. When animals die, they decompose and the
phosphorus is returned to the soil to be used
again.

49. Long term cycle
Phosphates washed into water become
incorporated into rock as insoluble compounds.
Millions of years later, as the environment
changes, the rock containing phosphorus is
exposed. As the rock erodes, the phosphorus
again becomes part of the local ecological
system.