CHAPTER 2
PRINCIPLES OF ECOLOGY
ORGANISMS AND THEIR
RELATIONSHIPS
• Main Idea for Ch. 2.1:
–Biotic and abiotic factors interact in
complex ways in communities and
ecosystems.
• Discussion:
–Who or what do you
depend on?
• ECOLOGY
– Ecology is the scientific area in which the
relationships among living organisms and the
interactions the organisms have with their environments
are studied.
• Scientists who study ecology are called ecologists.
– Ecologists perform tests in the environment where
organisms live to find out why they die or live, grow in
number or decrease, live in water or near the water, etc.
– Ecologists use models so they can test in a lab things that
are happening in the environment.
» Models help scientists control the variables and study
them one at a time.
• EX: more or less water, more or less light,
temperature changes, etc.
» Helps scientists completely understand the effects
taking place in the environment.
• Discussion:
• Which task would be completed by an ecologist?
– Survey and classify mollusk fossils
– Inoculate cattle against infection
– Test the effect of cyanide on algae
– Explore the medicinal uses of nectar
• What are some locations where you might find
ecologists collecting data, and what tools might
they use in these locations?
• What types of organisms have you ever observed or
collected that live near your home?
• What are some interesting characteristics of these
organisms?
• THE BIOSPHERE
– Biosphere is the portion of Earth that supports life.
• The prefix “bio” means life.
• Includes: surface of earth, atmosphere, oceans, lakes, and
extends down several kilometers below the surface to any
location that includes life.
• EX:
Rainforest
Desert
Marine Life
• Ecologists study these organisms, their adaptations, and the
factors in their environments.
– These factors are divided into 2 large groups.
» Living factors – biotic
» Nonliving factor - abiotic
• BIOTIC FACTORS
• Anything living in an organism’s environment are
called biotic factors.
– The interactions among organisms are necessary for the
health of all species in the same geographic location.
– What are some of the biotic factors in this picture and
how do they relate to one another.
• ABIOTIC FACTORS
– Nonliving factors in an organism’s environment are called
abiotic factors.
– Abiotic factors include:
•
•
•
•
•
•
•
Temperature
Air
Water
Sunlight
Soil types
Rainfall
Nutrients
– Organisms depend on abiotic factors to survive.
– Organisms have adaptations to live with certain abiotic
factors. If the abiotic factors change organisms need to
change or they will die.
– Argument: Oxygen is the only abiotic factor that allows you
to survive in this classroom. So, as long as there is enough
oxygen, all of you will survive.
• LEVELS OF ORGANIZATION
• Levels of organization increase in complexity as the
numbers and interactions between organisms
increase.
• Levels of organization are:
– Organism
– Population
– Biological community
– Ecosystem
– Biome
– Biosphere
• ORGANISMS, POPULATIONS, AND BIOLOGICAL
COMMUNITIES
• Organism – is one individual
• Population – is a single species that share the same
geographic location at the same time.
– Individual organisms in the population
compete for the same resources. If the
resources are high, the population will grow. If not, the
population will decrease. Eventually the population #’s
will match the resources for the area.
• Biological community is a group of interacting
populations that occupy the same geographic area
at the same time.
– Different populations may or may not compete
for resources.
• ECOSYSTEMS, BIOMES AND THE BIOSPHERE
• Ecosystem is a biological community
including the abiotic factors that affect it.
– Ecosystems can be large or small
• Biome is a large group of ecosystems that share the
same climate and have similar types of
communities.
• Biosphere contains all of the biomes on Earth and is
the highest level of organization.
• ECOSYSTEM INTERACTIONS
• Survival of the different populations increases if
they use the resources in different ways.
– EX: birds use different areas of the tree to build nests.
• Habitat is an area where an organism lives.
– EX: deer covering 5 sq. miles to find food.
• Niche is the role or position that an organism has in
its environment (habitat).
– EX: food, shelter, and reproduction
• Discussion:
– What is an example of a habitat and an individual’s niche
in that habitat?
• COMMUNITY INTERACTIONS
• Interactions in the community include
competition for basic needs like food,
shelter, mates, and how organisms
depend on each other for survival.
• COMPETITION
– Competition occurs when more than 1 organism
uses the resource at the same time.
• The organism that out competes the other one
is the one that survives.
• PREDATION
– Predation is when one organism pursues and eats
another organism for food.
• Predator is the organism that is
doing the pursuing.
• Prey is the organism that is caught and ate.
• EX: mallard duck eating water bug.
• SYMBIOTIC RELATIONSHIPS
• Symbiosis is the close relationship that exists when 2 or
more species live together.
• There are 3 different types of symbiosis:
– Mutualism
• Both organisms receive a benefit
–EX: flowers and bees
– Commensalism
• One organism receives a benefit & the other one is
not hurt or harmed
–EX: clownfish and sea anemones
– Parasitism
• One organism receives the benefit & the other one is
hurt or dies.
Section 2.2
• FLOW OF ENERGY IN AN ECOSYSTEM
• Autotrophs capture energy, making it
available for all members of a food web.
• The sun is the original source of energy!
• ENERGY IN AN ECOSYSTEM
• Organisms differ in how they obtain energy. They are
either autotrophs or heterotrophs.
• AUTOTROPHS
– Autotrophs are organisms that collect energy from
sunlight or inorganic substances to produce food.
• EX: plants, bacteria
– Autotrophs are the foundation for all organisms in an
ecosystem
– Autotrophs are also called producers
• Discussion: What is the process by which autotrophs
convert light energy into chemical energy?
• HETEROTROPHS
– Heterotroph is an organism that gets energy by
consuming other organisms.
– Heterotrophs are also called consumers.
– Different types of consumers:
•
•
•
•
Herbivore – only eats plants, EX: rabbit, cow
Carnivores – only eat meat, EX: wolves, lions
Omnivores – eat both meat & plants, EX: humans, bears
Detritivores - eat fragments of dead matter in an ecosystem
and return nutrients back to the soil, air, and water where the
nutrient can be recycled by other organisms. EX: worms
• Decomposers (similar to detritivores) – break down dead
organisms by releasing digestive enzymes. EX: fungi
(mushrooms), bacteria
• MODELS OF ENERGY FLOW
–Ecologists use food chains & food
webs to model the energy flow
through an ecosystem.
–A trophic level is a step in a food
chain or web.
–Autotrophs make up the first
trophic level in all ecosystems.
–Heterotrophs make up the
remaining levels.
• FOOD CHAINS
• Food chain is a simple model that show how energy
flows through an ecosystem.
• In a food chain the energy ONLY
flows in one direction, up the
tropic levels.
• The arrows show what direction
the energy flows, which usually
starts with the autotrophs and
moves to the heterotrophs.
• Some of the energy is not
transferred from one trophic level
to the next because it is used by the organism for
new cells & tissues.
• FOOD WEBS
• A food web is a model representing the many
interconnected food chains and pathways in which
energy flows through a group of organisms.
http://www.goldridge08.com/foodchain.htm
• ECOLOGICAL PYRAMIDS
– An ecological pyramid is a diagram that shows the
relative amounts of energy biomass or numbers or
organisms at each trophic level in an ecosystem.
– Energy pyramid only 10% of the energy is transferred to
the next level.
• The organism uses 90% of the energy for
bodily processes or released as heat.
– Biomass pyramid shows the amount of total mass of
living matter at each trophic level
– Pyramid of numbers shows the number
of organisms at each trophic level
SECTION 2.3
• CYCLING OF MATTER
–Essential nutrients are cycled through
biogeochemical processes.
• Discussion:
–What would happen if matter was
bound in living matter and never
recycled?
• CYCLES IN THE BIOSPHERE
• Energy is transformed into usable forms to support life of an
ecosystem.
– Constant supply needed so matter needs to be recycled.
• Matter is anything that takes up space and has mass.
• Nutrient is a chemical substance that an organism must obtain from
its environment to sustain life and to undergo life processes.
• Biogeochemical cycle is the exchange of matter through the
biosphere.
– Bio means life, geo means earth, & chemical
– Producers (plants) use air, soil and water to convert them into
usable nutrients. Consumers eat the plants & the nutrients are
passed to them. Decomposers will return the nutrients to be
recycled.
• WATER CYCLE
• Water is constantly evaporating off of bodies of
water & go up into the atmosphere in the form of
water vapor.
– 90% of all evaporation occurs over the ocean,
lakes and rivers.
– 10% evaporates from plants through a process
called transpiration.
• Water vapor creates clouds & then precipitation.
• Ends up on the surface & is soaked up by plants or
remains underground. Can fall in lakes or streams &
return to ocean
• THE WATER CYCLE - CONTINUED
• Organisms cannot live without water.
• 3% of all water on Earth is fresh. 69% of all fresh
water is either frozen in glaciers or underground.
• THE CARBON AND OXYGEN CYCLES
• All living things are composed of molecules that contain
carbon, such as protein, carbohydrates and fats.
• Carbon and oxygen make up molecules essential for
life, including carbon dioxide and simple sugars.
• In photosynthesis, plants and algae, will convert carbon
dioxide + water into carbohydrates + oxygen for the
atmosphere.
– These carbohydrates are used as a source of energy for all
organisms in the food web.
– Carbon dioxide is recycled back into the atmosphere through
cellular respiration. (You do cellular respiration)
• Carbon can be stored for long periods of time as fossil
fuels & released when burned, adding carbon dioxide
to the atmosphere.
• Discussion:
– Based on your understanding of the carbon cycle,
predict what might happen if large areas of tropical rain
forest continue to be cleared.
– How do you interact in the carbon cycle?
• THE NITROGEN CYCLE
• Nitrogen is an element.
• Largest amount found in atmosphere.
– Can’t be used by plants and animals in this form
• Nitrogen fixation occurs when bacteria convert the
nitrogen gas to nitrates.
– Enters food web when plants absorb nitrogen compounds
from the soil & convert them into protein.
– Nitrogen is often a limiting nutrient for the growth of
producers.
– Decomposers will return nitrogen in protein back into
ammonia.
• Denitrification occurs when bacteria convert the
nitrogen compounds back into nitrogen gas returning it
to the atmosphere.
• NITROGREN CYCLE
• THE PHOSPHORUS CYCLE
• Phosphorus essential for growth & development of
organisms.
• Short term cycle:
– Soil →producers →consumers
– Decomposers return phosphorus to soil
• Long term cycle:
– Stored in sedimentary rocks
– Released through weathering
or erosion
• Phosphorus is a limiting nutrient.