Unit 7: Ecology
Chapter 18: Ecosystems and Human Population
I. Section 18.1: Ecosystems:
1. An ecosystem is made up of _________________ creatures and the
_________________ things that those creatures need within an area.
2. _______________ moves through an ecosystem in one direction.
B. Biological Communities:
1. A ___________________ consists of all individuals of a single species that occur together at a
given place and time.
a. A single type of organism that can interbreed and produce fertile offspring.
b. All the populations living together in the same area make up the community.
c. An ecosystem is all of the living things in a community and the physical and chemical
factors that they interact with.
C. In an Ecosystem:
1. ________________ factors – the living organisms within an ecosystem
a. Examples: Bacteria, Algae, Plants, Animals
2. _______________ factors – physical and chemical features
a. Example: light, oxygen, water, carbon dioxide, good soil
b. Living space and the right temperature range
1. _______________ - A species’ way of making a living
a. Example: Making a living as a top carnivore an animal that eats other animals, but is
not eaten by any other animal.
2. Every species fills a niche, and niches are almost always filled in an ecosystem.
1. ______________ - where an organism lives
2. The important characteristics of a habitat include; climate, the availability of food, water, and
other resources, as well as other factors, such as weather.
F. Roles in Ecosystems:
1. As with biomes, ____________ conditions determine which ecosystems are found in which
2. A particular biome encompasses all of the ecosystems that have similar climate and
3. Different organisms live in each different ecosystem.
4. Every ecosystem has the same general roles that living creatures fill:
a. It’s just the organism that fills those niches that are different
b. Example: Every ecosystem must have some organisms that produce food in the form
of chemical energy (primarily algae in the oceans, plants on land, and bacteria in the
G. Producers and Consumers:
1. _____________________ - the organisms that produce food are extremely important in
every ecosystem. These organisms produce their own food.
2. Two ways of producing food energy.
a. _____________________________ - on land in plants or phytoplankton on the
b. _____________________________ - bacteria at hydrothermal vents
3. _____________________ - organisms that use the food energy that was created by
a. ____________________ - eat producers directly
b. ____________________ - eat animals
c. ____________________ - eat plants and animals
H. Feeding Relationships:
1. Many types of feeding relationships:
I. Flow of Energy in Ecosystems:
1. The ____________________ create chemical energy from abiotic factors (including solar
2. The food energy created by producers is passed to consumers, scavengers, and decomposers
3. __________________ level (energy level) – energy flows through an ecosystem in only
__________ direction, energy is passed from one organisms (trophic level) to another organism
in the next trophic level.
4. Most of the energy (about 90%) is used in the trophic level – ONLY 10% of the energy is
passed to the next trophic level.
J. Food Chains:
1. _________________________ - the set of organisms that pass energy from one trophic level
to the rest.
2. A top predator must have a very large range which to hunt so that it can’t get enough energy
K. Food Webs:
1. ________________________ - recognizes that many organisms eat at multiple trophic levels
2. Food webs are interconnected
a. Example: Birds or bears that live on land may eat fish, which connects the two food
3. Humans are an important part of food webs
a. Some believe that since nothing “eats” us we are the top predators
L. Food Web Practice:
1. List the producers:
2. What trophic level would the grasshopper be found at?
3. What would the top predators be? What do they eat?
M. Flow of Matter in Ecosystems:
1. ___________________ are ions that are crucial to the growth of living organisms
a. Nitrogen and phosphorous are important for plant cell growth
2. The flow of nutrients in an ecosystem is not like the energy flow
a. ___________________ enters an ecosystem at any level and leaves at any level
b. Matter cycles freely between trophic levels and between the ecosystem and the
3. Rocks and minerals break down to release nutrients
a. Nutrients can be brought in from other regions
b. Nutrients can also cycle out of an ecosystem
4. ____________________________ a key role in making nutrients available to organisms
N. Relationships Between Species:
1. ________________________ - occurs between species that try to use the same resources
a. When there is too much competition, one species may move or adapt so that it uses
slightly different resources.
2. _____________________ actions improve a species’ survival
a. Example: One deer warns the other of predators in the area
b. Example: Individual ants perform different tasks required for the survive of all
3. Each niche can only be inhabited by one species – some relationships between species are
beneficial to at least one of the two interacting species – called ________________.
a. _______________________ - the relationship that benefits both species
b. _______________________ - one organism benefits and the other is not harmed
c. _______________________ - the parasite species benefits and the host is harmed
II. 18.2: The Carbon Cycle and the Nitrogen Cycle:
1. _________________ is a very important element to living things.
a. Carbo occurs in many forms on Earth and is found throughout the environment.
b. The element moves through organisms and then returns to the environment – when
all this is balanced, the ecosystem remains in balance too.
2. ________________ is also a very important element, used as nutrients for plant and animal
B. Short Term Cycling of Carbon:
1. Through ___________________________, the inorganic carbon dioxide plus water and
energy from sunlight is transformed into organic carbon (food).
2. Plants and animals engage in the reverse of photosynthesis, which is
3. Photosynthesis and respiration are gas exchanges.
C. Human Actions Impact the Carbon Cycle:
1. Humans have changed the natural balance of the carbon cycle because we use coal, oil, and
natural gas to supply our energy demands.
2. The second largest source of atmospheric ____________ is ___________________________.
a. Trees naturally absorb CO2 while they are alive
b. Trees that are cut down lose their ability to absorb CO2
D. Why is the Carbon Cycle Important?
1. Carbon dioxide is a _______________________ gas so it absorbs infrared energy, the longer
the wavelengths of the Sun’s reflected rays.
2. When greenhouse gas levels in the atmosphere _____________________, the atmosphere
holds onto more heat than it normally would.
a. This increase in global temperatures is called global warming.
E. The Nitrogen Cycle:
1. ________________ (N2) is also vital for life on Earth as an essential component of organic
materials (amino acids, nucleic acids, and chlorophyll)
2. Although nitrogen is the most abundant gas in the atmosphere, it is not in a form that plants
can use, so it has to be “fixed”.
3. Usable nitrogen is sometimes the factor that limits how many organisms can grow in an
III. 18.3: Human Populations:
1. Improvements in agriculture, sanitation, and medical care have enabled the human
population to grow enormously in the last few hundred years.
2. As the population grows, consumption, waste, and the overuse of resources also grow
1. ________________ and ________________ factors determine the population size of a
species in an ecosystem.
2. When does a population grow?
3. When does a population shrink?
4. For a population to grow there must be ample resources and no major problems
5. For a population to shrink it can be due to either _____________ or _____________ factors
a. An _________________ in predators, the emergence of a new disease, or the loss of
b. It could shrink if it grows too large for the resources required to support it
C. Carrying Capacity:
1. When the _________________________ of births equals the number of deaths, the
population is at its carrying capacity.
a. There are as many organisms of that species as the habitat can support
2. If these factors improve, the carrying capacity ___________________
3. If these factors become less plentiful, the carrying capacity __________________
4. If resources are being used ___________________ than they are being replenished, then the
species has exceeded its carrying capacity.
5. If this occurs the population will then decrease in size.
D. Limiting Factors:
1. Every stable population has one or more factors that limit its growth
a. Can be any biotic/abiotic factor (nutrient, space, water)
b. The size of a population is tied to its limiting factor
2. If a limiting factor increase a lot then another factor will become the new limiting factor.
IV. Types of Biomes: Terrestrial (Land) Biomes:
A. Information to Know:
1. Factors that affect biomes climate:
2. Major biomes – large areas with similar climates and ecosystems
B. Tundra - _________________________________________________________________________
C. Taiga - ___________________________________________________________________________
D. Temperature Deciduous Forest - ______________________________________________________
E. Temperature Rain Forest - ___________________________________________________________
F. Tropical Rain Forest - _______________________________________________________________
G. Desert - __________________________________________________________________________
H. Grasslands - _______________________________________________________________________
V. Aquatic Biomes:
A. Freshwater Ecosystems – include flowing and standing water, low to no salt
B. Rivers and Streams – flowing water
1. Most of the ______________________ are washed into the water from land
2. The faster the flow, the greater the oxygen content
C. Lakes and ponds – very little flow
1. Sunlight warms and lights the pond bottom, supporting plant and animal life
2. Deeper lakes support life along shallow shoreline or surface.
D. Water pollution – a problem caused by fertilizer – filler runoff and sewage
E. Wetlands – regions wet all or most of the year
1. Lie between solid land and water
2. Very fertile ecosystems
F. Saltwater Ecosystems – 95% of Earth’s water contains high concentration of salt, or high salinity
G. Open Oceans – divided into light and dark zones
1. Lighted – the upper 200m and home of plankton
2. Dark – below 200m where animals feed on material that floats down or prey on each other
H. Coral Reefs – diverse and fragile ecosystems formed from coral shells of calcium carbonate
I. Seashores – along coastlines
1. Intertidal Zone – covered with water at high tide and exposed to air at low tide
2. Drastic changes in temperature, moisture, salinity, and wave action
J. Estuaries – where a river meets ocean; called bays, lagoons, harbors, inlets, sounds
1. Rich in nutrients
2. Changing mixture of salt water and freshwaters