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UNIT 7 – EVOLUTION
Essential Questions
 How do living things obtain, use and transfer energy?
 What causes an ecosystem to be stable and well-balanced?
 What causes ecosystems to change?
 How do ecosystems respond to change?
 What does it mean to be “green”?
What Students Should Know
 A population is defined as all the members of a species, in a defined area, at a
given time.
 Members of a population will compete for resources with other members of that
population along with other species.
 As any population of organisms grows, it is held in check by interactions among a
variety of biotic and abiotic factors.
 An ecosystem consists of all the interacting species and the abiotic environment in
a given geographic area.
 Ecosystems demonstrate an exchange of energy and nutrients among inhabiting
organisms.
 Energy flows through an ecosystem; it does NOT cycle. It begins with the sun’s
light energy that is absorbed by producers and converted to chemical energy in
the form of glucose.
 Nutrients cycle through an ecosystem. The most common examples include
carbon, oxygen, nitrogen, and water.
 Ecosystems demonstrate an exchange of energy and nutrients among inhabiting
organisms. Only about 10% of the energy of the energy available within one
tropic level is transferred to organisms at the next tropic level. Mores links a food
chain means a higher amount of producer energy needed to sustain it.
 Flow of energy occurs between trophic levels in all ecosystems and can be
depicted as follows:
 food chain
 food web
 pyramid of energy
 pyramid of biomass
 pyramid of numbers.
 The reproductive rates of a species will affect its population growth. Some
organisms reproduce rapidly (r-strategists) while others reproduce more slowly
(K-strategists).
 The average number of population that can live in a given area at a given time is
known as the carrying capacity of that ecosystem. This number is not rigid, but
fluctuates due to reproduction, death and changing environmental conditions.
 The gradual change in an ecosystem that occurs as communities slowly replace
one another is known as ecological succession.
 Ecological succession is a series of changes in a community in which new
populations of organisms gradually replace existing ones. Primary succession
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begins when a pioneer community enters a barren area. Secondary succession
occurs where an existing community has been partially destroyed.
A climax community occurs when succession slows down and a stable
community is established. The climax community is made up of organisms that
are successful at competing for resources in a given environment. The climax
community in most of Virginia is a deciduous oak-hickory (hardwood) forest.
The combination of average precipitation and temperature define major
geographic areas called biomes. Biomes are defined by their predominant plant
species, which is determined by the climate.
Two different species can live in a close relationship called symbiosis. The three
types of symbiotic relationships are commensalism, mutualism and parasitism.
As the human population increases, so does human impact on the environment.
Human activities such as reducing the amount of forest cover, increasing the
amount and variety of chemicals released into the environment, and intensive
farming have changed the Earth's land, oceans, and atmosphere. Some of these
changes have decreased the capacity of the environment to support some life
forms.
A current global issue is the greenhouse effect. The basic idea is that human
action has resulted in an unnatural increase in the amount of carbon dioxide in the
atmosphere. This extra carbon dioxide traps the sun’s energy, increasing the
temperature of the earth. Results may include changing weather patterns, arid
agricultural lands, melting ice caps and glaciers causing rising sea levels.
Biodiversity refers to the number of different species that live together in a given
area.
What is Ecology??
•The
study of interactions that take place between organisms and their
environment.
•It explains how living organisms affect each other and the world they live in.
Habitat & Niche
•Habitat - the place a plant or animal lives
•Niche - an organism’s total way of life
The Nonliving Environment
•Abiotic factors - the nonliving parts of an organism’s environment.
•Examples include air currents, temperature, moisture, light, and soil.
The Living Environment
•Biotic factors- all the living organisms that inhabit an environment.
•All
organisms depend on others directly or indirectly for food, shelter,
reproduction, or protection.
Levels of Organization -
•Atom
Molecule
Organelle
Population Community
Cell
Tissue
Organ
System
Organism
•Ecologists have organized the interactions an organism takes part in into different levels
according to complexity:
1st Level of Organization = Organism - An individual living thing that is made of cells,
uses energy, reproduces, responds, grows, and develops
2nd Level of Organization = Population- A group of organisms, all of the same species,
which interbreed and live in the same place at the same time.
3rd Level of Organization = Biological Community - All the populations of different
species that live in the same place at the same time.
4th Level of Organization = Ecosystem - Populations of plants and animals that interact
with each other in a given area with the abiotic components of that area. (terrestrial or
aquatic)
5th Level of Organization = Biosphere - The portion of Earth that supports life.
The Biosphere- Life is found in air, on land, and in fresh and salt water.
Community Interactions
 Competition
 Predation
 Symbiotic Relationships:
o Mutualism
o Commensalism
o Parasitism
Energy Flow In Ecosystems
 Producers/Autotrophs capture energy from the sun and make it available for other
members of an ecosystem.
 Food chains vs. Food webs
Nutrients Cycle Through Ecosystems
 Biogeochemical cycles
o Water Cycle
o Carbon Cycle
o Nitrogen Cycle
o Phosphorous Cycle
Critical Thinking Diagram Worksheet – Food Web
Critical Thinking Diagram Worksheet – Food Web Answers
Use the information shown in the diagram to complete the following.
1. Identify a food chain that consists of only a producer, a primary consumer, and a
secondary consumer.
Answers may vary
2. Identify a food chain that consists of a producer, a primary consumer, a secondary
consumer and a tertiary consumer.
Answers may vary
3. What is an herbivore? An organism that eats plants
Identify three herbivores shown in the diagram. Answers may vary
4. What is a carnivore? An organism that eats meat
Identify three carnivores shown in the diagram. Answers may vary
5. Add decomposers to the food web by writing the term Decomposers in the correct
place and adding arrows as appropriate.
6. What do the arrows indicate about the flow of energy through the community?
Arrows point in the direction of the energy flow.
FOOD CHAIN AND FOOD WEB ONLINE WEBQUEST
Food Chain and Food Web Online Quest Answers
Part One:
http://www.ecokidsonline.com/pub/eco_info/topics/frogs/chain_reaction/index.cfm
1.Click on “PLAY THE GAME”
2.Click on “START”
3.What is the MAIN purpose of eating food? To get energy
10. What is an omnivore? An organism that eats plants and animals. Give an example
Answers may vary
4.Click Next
5.What is a carnivore? An organism that eats only meat. Give an example Answers
may vary
7. Click Next
8. What is a herbivore? An organism that eats only plants. Give an example Answers
may vary
9. Click on Next
10. Where do plants obtain their energy? Sun, water & soil
6.What is a food chain? The order that animals feed on other plants and animals.
Click on “FOREST FOOD CHAIN”
13. Try to drag the animals in its correct order from producers to consumers. When you
think you have it correct, click on “TEST THE FOOD CHAIN.” Once you have the
correct order place the correct numbers below (1-producer, 2- primary consumer, etc.)
_6_ owl ___5__ snake ___2__ grass ___4___ frog ___3__ grasshopper __1___sun
14. Describe in your OWN words what would happen if you take the frog out of the
food chain? (click on “CLICK ON THE FROG TO FIND OUT” )
Answers may vary
Part Two:
http://www.vtaide.com/png/foodchains.htm
1.In your own words, describe why the further along you go in a food chain the less
food remains? A large amount of energy is lost as you go up each link or level, so less
and less energy is transferred.
2. In your own words, describe why food chains do not have more than four/five links?
Less and less energy available with each link.
Part Three:
http://drake.marin.k12.ca.us/stuwork/rockwater/PLANKTON/Food%20Chain.htm
1. Look at the diagram, write the animal that corresponds to the correct word:
Phytoplankton
Producer
Zooplankton
Primary Consumer
Small Fish
Secondary Consumer
Bigger Fish
Tertiary Consumer
Mammal
Quaternary Consumer
Part Four:
http://library.thinkquest.org/11353/food.htm
1. What provides all ENERY for every organism? The sun
2.
In your own words, how have humans affected the food chain process? We
have been breaking links in the food chain as animals go extinct due to
human impact.
Ecological Succession
Communities do not remain the same but change over a period of time. This is mostly
because of a process called ecological succession. We see this process all around us as
abandoned farmland changes to weed fields, brush land and finally to a forest.
One community succeeds another in several stages as conditions change that favor
another suite of wildlife species.
The first stage in succession is called the pioneer stage, which consists of bare habitat
conditions, such as exposed rock. This stage remains until conditions change to the point
that soil accumulates and plants are able to grow.
These changes continue until formation of a climax community, which is in equilibrium
with soil and climatic conditions. Species of a climax community do not create conditions
unfavorable to themselves or more
favorable to other species.
Bare Ground
Grassy-Weedy Brushy Young
(Stage 1) (Stage 2)
(Stage 3)
Woodland
(Stage 4)
BIOME CHART
Mature Woodland
(Stage5)