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?

• 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.–EX: Fleas, ticks, tapeworms, etc.

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.