Biology 11
What is Ecology?
• the study of the interactions that take place
between organisms and their environments
The Biosphere
• The part of the Earth that supports living
Non-Living Environment
• Abiotic factors are non living parts of an
• Often determine which species survive in a
certain environment
• Include air currents, temperature, moisture,
light, and soil
Analyzing Graphs
• Question: How does an abiotic factor affect food
• Green plants carry out the process of
photosynthesis. Glucose, a sugar, is the food
product made during this process. Glucose
production can be used as a means for measuring
the rates at which the process of photosynthesis is
• Examine the following graph of a plant called
1. What is the abiotic factor influencing
photosynthesis? How does this factor affect
2. How much glucose is being produced at 20
3. Based on the graph, at which temperature is glucose
production greatest?
4. Does the graph tell you how the rate of
photosynthesis might vary for plants other than
saltbrush? Explain your answer.
What happens to the formation of glucose after
the temperature reaches 30 degrees?
• A complete study of an organism includes
examination of the abiotic factors influencing
the organism
Ex. Study of salmon life cycle would include
whether needed to lay eggs on rocky or sandy
stream bottoms
Living Environment: Biotic Factors
• All living organisms that inhabit the
environment are called biotic factors
• All organisms depend on others either directly
or indirectly
– Food, shelter, reproduction, protection…
Levels of Organisation
• Population
– A group of organisms of the same species that
interbreed and live in the same area at the same time
– Members of a population may compete for resources
(food, water, mates, habitat…)
• Communities
– Made up of interacting populations in a certain
area at a certain time
• Ex. Birds eating insects, mushrooms growing on
decaying leaves
– A change in one population within a community
may cause changes in other populations
• Ecosystem
– Made up of interacting populations in a biological
community and the community’s abiotic factors
• 2 major kinds of ecosystems:
Rotting log
Aquatic (Salt
Intertidal Zone
• Means living together
• Is the relationship in which there is a close and
permanent association between organisms of
different species
• Includes mutualism, commensalism,
Mutualism (+/+)
• Both species benefit from association
• Example: Ants and Acacia trees
Commensalism (+/0)
• One species benefits, the other species is
neither harmed nor benefitted
• Example: Remora fish
Parasitism (+/-)
• Harmful to one species but beneficial to the
• Evolved relationship where parasite harms,
but does not usually kill host
• Example: Tick
Brood Parasitism
• Ex. Brown-headed cowbird
– Lay eggs in nests of song birds
Other interactions…
• Competition
– Between individuals of the same species or
between different species
– For resources such as food, water, sunlight, space
• Predation
– One individual eats all (or part) of another
• A behaviour that may be a disadvantage to the
individual, but benefits other
• Or… a behavioural that is detrimental to the
individual but favours the survival of that
individuals genes through relatives
Ecosystems Change over Time
• Succession: orderly, natural changes and
species replacement that take place in the
communities of an ecosystem
• Takes place in stages
• Different species of plants and animals may be
present at each stage (different conditions)
• Takes place over decades or centuries
• 2 types of succession
1) Primary Succession
• Colonization of barren land (no living
• Examples: Following volcanic eruption or
retreat of glacier
• First species to take hold are pioneer species
(ex. Lichens)
• Pioneer species eventually die, decay, and
change the landscape for the next stages
• Over time a climax community matures
• This community is stable and undergoes little
or no change
• Could last hundreds of years
2) Secondary Succession
• Sequence of changes that takes place after an existing
community is severely disrupted (ex. Forest Fire)
• During succession the community of organisms
inhabiting an area gradually changes
• Secondary succession takes place in a region that
previously contained life, and still contains soil.
• Involves different pioneer species and takes less time to
reach climax community than primary succession
Interpreting Scientific Illustrations
• Succession is the series of gradual changes
that occur in an ecosystem. Ecologists
recognize two type of succession- primary and
• Examine the graph. The lines marked 1 and 2
represent primary and secondary succession
(but neither is defined for you)
1) Which line, 1 or 2, represents primary
succession? Secondary succession? Explain.
2) Which label, C or D, might best represent a
climax community? Pioneer organisms? Explain.
3) What does the sudden drop at point C
represent? What happens between D and E?
• Begin Ecology Questions
• Work on Vocab (due Friday)
Nutrient and Energy Flow
Biology 11
The Producers
• Autotroph- uses light energy or energy stored
in chemical compounds to make energy rich
• Ex. Grass and trees
• Process in chlorophyll that takes water, light,
and CO2 and produces sugar
• H2O + CO2 + light ---> C6H12O6 or glucose
• The sugar is then used as a building block for
amino acids, cellulose, or starch (for the plant
to use later)
Cellular Respiration
• C6H12O6 + O2 → CO2 + H2O + Energy
• H2O + CO2 + light ---> C6H12O6 or glucose
• C6H12O6 + O2 → CO2 + H2O + Energy
They keep making it, we keep breaking it down
(they break it down too)
The Consumers
• Organisms that get their energy from producers
• Primary consumers: Obtain energy by directly
consuming producer (herbivores)
• Secondary consumers: Obtain energy by eating
primary consumers (carnivores)
• Energy flow:
Producer Primary Consumer Secondary
Consumer  Tertiary/Quaternary Consumer
Decomposers- organisms that obtain energy
through the break down of non-living organic
materials (dead organisms)
– Include bacteria and fungi.
• Food Chain: simple model shows how matter
moves through an ecosystem
• Each organism in a food chain represents a
trophic level
• Food Web: show all possible feeding
relationships at each trophic level within a
Ecological Pyramids
• Shows how energy moves through an
• Base of pyramid represents autotrophs (1st
trophic level)
• Some of the energy transferred at each
trophic level enters the environment as heat
(less available at each higher level)
• ~10% of total energy is transferred from one
trophic level to the next
Pyramid of Numbers
Pyramid of Biomass
Pyramid of Energy
• Where would you expect the largest biomass?
• What do you think the world’s largest
organisms eat? Why?
Biogeochemical Cycles
• Organisms not only need energy for survival,
but also nutrients
• Water, Phosphorous, Nitrogen, Carbon
Dioxide, and Oxygen are all cycles in the
• These nutrients move through the biosphere
differently than energy
Limiting Factors
• Are factors that affect an organism’s ability to
survive in its environment
• Include water, food, predators, temperature
• Limiting factor: any biotic or abiotic that
restricts existence numbers, reproduction, or
distribution of organisms
Common Limiting Factors
Soil Chemistry
Other Organisms
• Do questions page 1027 #1, 2, 4, 5 and page
1030 #1-8, TF 1-8, CM # 1, 2, 4, 7, 8
• Activity: Birds, Bugs, or Beans
• Human Population Growth
Population Growth
How many people can the Earth hold?
Biology 11
Principles of Population Growth
• Population: a group of organisms of the same
species that live in a specific area
• Healthy populations will grown and die at a
steady rate (unless it runs out of resources, is
attacked by predators or disease)
• What would you expect population growth to
look like if resources were abundant? Graph it.
Exponential Growth
• The growth of a population starts slowly, then
begins to look like a J-shaped curve
• Initial growth is slow because the number of
reproducing individuals is small
• Rate of population growth increases because
the total number of individuals able to
reproduce has increased
• This is exponential growth
• Is growth unlimited?
• No: different limiting factors (resources,
predators, disease…)
• Under these pressures, populations may
stabilize into an S-shaped growth curve
Carrying Capacity
• The number of organisms of one species than an
environment can support indefinitely
• If a population is in an environment with resources,
there are more births than deaths and population
will increase until carrying capacity is
• When population overshoots the carrying
capacity, limiting factors have effect
• Deaths exceed births and lower population
below carrying capacity
What might be some limiting factors?
Factors Affecting Population Growth
• Limiting factors: biotic or abiotic factors that
determine whether an organism can live in a
particular environment
• There are two kinds of limiting factors that are
related to dispersal
– Density-dependent factors
– Density-independent factors
• Population Density: number of individuals in a
given area
Density Dependent
• Have increasing affect as population density
• Includes disease, competition, predators,
parasites, food, crowding
• When populations become crowded,
organisms compete for food, water space,
sunlight and other essentials.
• Competition among members of the same
species is a density-dependent limiting factor.
• Populations in nature are often controlled by
• The regulation of a population by predation
takes place within a predator-prey
relationship, one of the best-known
mechanisms of population control.
Parasitism and Disease
• Parasites can limit the growth of a population.
• A parasite lives in or on another organism (the
host) and consequently harms it.
Density Independent
• Can affect populations regardless of density
• Most are abiotic factors
– Volcanic eruptions, temperature, storms, floods,
drought, chemical pesticides, and major habitat
• Human Population Clock
Crops are on the rise, and we use
them poorly…
• The combination of growing corn, beans, and
squash, produces a average total of 2.7 million
calories per acre or enough with all arable land in
production to feed 2.5 times the population in
• The USDA accepted 3.9 million new acres into the
Conservation Reserve Program, or CRP, in the
latest sign-up period and turned away 600,000