Biology : Ch. 15 : Ecology
(Populations)
Our next unit of
study will be
Ecology.
Ecology is the
study of
interactions
between animals
and their
environment.
Population
A population is
described as
individuals of a species
that live together and
naturally reproduce.
Journal Activity #1
Identify a local population. Explain its range and
habitat.
Population Features
The number of individuals
in a population is its size.
The number of individuals
living in a given area is the
density.
The arrangement of
individuals in a population
is called its dispersion.
Population Growth
Populations grow in an
exponential manner.
The population size
that an environment
can sustain is called the
carrying capacity.(K)
Population Control
Populations are
controlled by the
resources available :
food, water.
These resources which
control populations are
termed density
dependent factors.
Population Control
Other factors such as
weather and climate
control populations.
These are called
density independent
factors.
Mosquitoes
Population Growth
Some species show
rapid population
growth (r-strategists)
insects, etc.
Other species show
slow growth.(K-
strategists)
Journal Activity #2
Identify the following as r or K strategist species.
* cats
* humans
* rabbits
* mayflies
* grasses
15-2 How Populations Evolve
Populations change
over time by a change
in the frequency of
alleles and genes.
Natural selection is
thought to be the force
which “drives” this
change in alleles and
genes in a population.
Hardy – Weinberg Principle
This principle states
that the allele
frequency in a
population doesn’t
change unless acted
upon by an outside
process. (Natural
Selection)
Evolutionary Forces
There are thought to be
5 evolutionary forces:
Gene flow
Nonrandom mating
Genetic drift
Natural selection
mutation
Evolutionary Forces
Gene flow: the
movement of alleles
into or out of a
population
Mutation: a change in
DNA
Nonrandom mating:
preferences based upon
a phenotype or
behavior
Evolutionary Forces
Genetic Drift:
changes in a
population based
upon a chance
event.(usually small
populations)
Natural Selection:
selection of genes
by the environment
which cause greater
survival and
reproduction
Gene Persistance
Some genes persist due
to “carriers”.
Harmful genes can
cause death when an
individual is
homozygous, but being
heterozygous keeps the
allele alive in a
population.
Ch. 16 : Ecosystems
The environment is
described as the
surroundings (living and
non-living) of an organism.
The living factors in an
environment are termed
biotic.
The nonliving factors in an
environment are termed
abiotic.
The biosphere is portion of
earth which supports life.
Journal Activity #1
In your journal titled Activity #1, make a data table
such as the one below. Identify 5 biotic and 5
abiotic factors in your environment and describe
the influence of six of these.
Biotic Abiotic
_____________________ _________________
_____________________ _________________
_____________________ _________________
_____________________ _________________
_____________________ _________________
Journal Activity #1 Cont…
Factor Influence on Your Life
_________ ___________________________
_________ ___________________________
_________ ___________________________
_________ ___________________________
_________ ___________________________
_________ ___________________________
Organization of Life: Levels
Biosphere
Ecosystems
Communities
Populations
Organism
Ecosystems
All biotic and abiotic
factors in an area form
an ecosystem.
Ecologists focus on
“ecosystem stability”.
Marine ecosystem
Communities
Communities may be
defined as several
interacting populations
which “share” their an
area.
Communities include
several different
species of animals,
plants, etc.
Populations
A population is
described as a group of
organisms of one
species living in the
same place at the same
time, which can
interbreed.
Organism
An organism is an
individual. The behavior
of an organism is often
studied in ecology.
Daily movement, feeding,
and breeding behavior may
be the topic of study of an
organism.
Organization of Life Summary
In ecology, many organisms make up a population,
many populations make up a community, an ecosystem
is a community with the environment, and the biosphere
is the total of all ecosystems on earth.
Organism-- Population -–Community--Ecosystem--Biosphere
Journal Activity #2
In your journal titled “Activity #2” describe the
following:
1) Identify a local ecosystem :
2) Identify 10 different animals and 5 different
plants in this community.
3) Identify and describe the effect of 3 different
abiotic and biotic factors on this ecosystem.
Niche/Habitat
A niche is the “role”
that a species plays in
their community.
A habitat is the place
where an organism
lives out its life.
Local “Turkey” Buzzard
Journal Activity #3
In your journal make a table as shown below.
Describe the niche and habitat of the species listed:
Species Habitat Niche
Blacktail deer ___________ _____________
Skunk ___________ _____________
Spiders ___________ _____________
Mice ___________ _____________
Canadian Goose ___________ _____________
You ___________ _____________
16-2 : Energy Flow in an
Ecosystem
Organisms interact with
each other in a variety of
ways.
These interactions allow
for organisms to obtain
energy, and control
populations of species.
The method in which
organisms obtain energy is
important in studying
ecology.
Obtaining Energy
Autotrophs: organisms
that use energy from the
sun to make their food.
(plants)
Heterotrophs: organisms
which depend upon
autotrophs as their food or
energy source.(animals)
Heterotrophs
Heterotrophs are
classified into other
categories based upon their
feeding habits.
Heterotrophs include the
following :
Carnivores
Scavengers
Omnivores
Decomposers How am I classified?
Carnivores
Carnivores : animals
that “kill” and eat other
animals or
heterotrophs.
*List some carnivores:
Scavengers
Scavengers: animals
which don’t kill their
food, but feed on dead
animals.
List some scavengers:
Omnivores
Omnivores: animals
which eat both plants
and animals.
Examples :
Humans
Racoons
Coyotes
Bears
Decomposers
Decomposers:
organisms which break
down compounds of
dead plants and
animals.
Examples : bacteria,
fungus, protists
Fungi are decomposers
Journal Activity #4
Using your resources to complete the following activity.
Make a list of 10 different animals found in the wetlands
around Dayton, and two different plants.
Use the internet and other sources to identify each animal as
to their feeding method : (carnivore, omnivore, scavenger,
decomposer)
Construct a simple feeding pyramid of the plants and
animals. (5pts)
Feeding Pyramid Example
Interactions of Organisms
While the predator-prey
interaction of organisms is
obvious, there are other
interactions involving
organisms.
Some organisms of
different species form
permanent associations.
These relationships are
known as symbiosis.
Symbiosis
There are three
different categories of
symbiosis.
Commensalism: one
species benefits, while
the other isn’t harmed
or benefited. Ex.) moss
on trees
Symbiosis
Mutualism: a type of
symbiosis in which
both organisms are
benefited.
Ex.) Lichen : an algae
and a fungus.
Symbiosis
Parasitism: a type of
symbiosis in which one
member is benefited,
while the other is
harmed.
Ex.) tapeworms,
roundworms, etc.
Tapeworm
Journal Activity #5
Use your resources to identify an example of each
type of symbiosis discussed : mutualism,
commensalism, and parasitism. For each type of
symbiosis include the following :
A) Identification of the two different species and the
type of symbiosis.
B) A brief description of the relation between the two.
Matter and Energy in
Ecosystems
Energy moves through an
ecosystem in a complex way.
In studying the overall health
of an ecosystem it is essential
to study the matter and
energy changes and
interactions in an ecosystem.
Food chains, food webs, and
food pyramids are tools used
to study matter and energy in
ecosystems
Food Chains
Food chains are
typically a simple
model which uses
arrows to show the
movement of matter
and energy in an
ecosystem.
Trophic Levels
Trophic levels are used
to study matter and
energy in an
ecosystem.
A trophic level is
described as a feeding
step of an organism.
Trophic Levels
Producers : (plants or
autotrophs) are assigned
trophic level 1
First order consumers:
animals which feed directly
on the producers are
trophic level 2
Second order consumers:
animals which feed on
other animals (carnivores)
are listed as trophic level 3
Trophic Levels
Tertiary consumer:
animal which feed on
second order
consumers, trophic
level 4.
Ex.) Sharks, Humans,
Bears, etc.
Journal Activity #6
In your journal construct a food chain, food web, or
pyramid for the following members in an
ecosystem. Identify the trophic levels. (5pts)
Animals : mice, rabbits, raccoon, deer, cougar, bear,
quail, bobcat, grasshoppers, snake
Plants: rye grass, blackberries, seeds
Energy Flow in an Ecosystem
As you go up a food
pyramid you find that the
energy in an ecosystem
greatly decreases.
There is much more energy
in trophic level 1 than in
trophic level 2 , etc.
Explain why energy
decreases as you go up
trophic levels?
Ecological Pyramids
Ecological pyramids can be
constructed to compare
populations and energy
amounts of trophic levels.
In an ecological pyramid
the 1st trophic level is on
the bottom, and the size of
the step represents the
amount of the population
or energy, or factor being
studied.
Cycling of Material in an
Ecosystem
Important nutrients,
and energy is cycled in
ecosystems.
Water cycle
Carbon cycle
Nitrogen cycle
Cycles
Water, carbon, and
nitrogen cycles allow for
the recycling of key
elements in an ecosystem.
Bacteria and other
organisms play an
important role in the
cycling of nutrients in an
ecosystem.
Journal Activity#7
Identify a cycle you will describe. ( water,
nitrogen, carbon, other)
Using the internet find a good diagram of the cycle
to copy and paste to a word document.
Give a detailed description of the cycle, and the
different stages of the cycle.
Describe the importance of this cycle to the cycling
of nutrients in an ecosystem.