Unit 2 CBA Review/Study Guide
Unit 2 Lesson 1
What Makes Earth a Habitable Planet?
A habitable planet has abiotic (nonliving) factors and
characteristics that are “just right” for allowing life to exist. In
our solar system, Earth is the only known planet at this time
with factors that are just right for allowing life to exist.
Factors that allow life on Earth:
 liquid water
 distance from Sun (93 million miles or 150 million km)
- if Earth was closer it would be too hot
- if Earth was further away it would be too cold
 temperature (0 OC - 100 OC) that allows for liquid water
to exist
 thicker atmosphere that protects us from harmful solar
radiation
 Earth’s atmosphere also contains elements and
compounds (in a gaseous form), such as nitrogen (N),
oxygen (O2), and carbon dioxide (CO2), needed to sustain
life
3
Unit 2 Lesson 2 Review/Study Guide
Dichotomous Keys
Biologists -scientists who study life and living organisms.
Sometimes biologists may observe an organism that is not
known to them. To help identify the unknown organism,
biologists use a tool called a dichotomous key.
Dichotomous key: is a series of choices (paired statements)
based on observations of physical characteristics.
The choices start with broad questions in which the object fits
into one of two categories. The next choice subdivides each of
the broad questions. Each set of questions becomes more
specific until the name of the object is reached.
1 Which of the following is most helpful for identifying an
organism using a dichotomous key?
A
Its average lifespan
B
Its sources of food
C
Its habitat
D
Its physical structures
2 A drawing of a leaf and a dichotomous key are provided.
What leaf is shown in the drawing?
A Liquidambar
B Magnolia
C Pine
D Redbud
3 An illustration of two insects is provided.
Which of the paired statements could be used to distinguish
the insects using a dichotomous key?
A Has 6 legs
Has 8 legs
B Large hind legs
Small hind legs
C 2 pairs of spots on wing cover
3 pairs of spots on wing cover
D Antennae absent
Antennae present
Unit 2 Lesson 3 Review/Study Guide
Microhabitats
Biotic factors = living things in an environment (plants/animals)
Abiotic factors = nonliving things in an environment (sunlight,
air, soil, water, temperature, rocks, etc.)
Habitat -the environment, or natural home, of plants, animals,
and other organisms
Microhabitat -smaller in size or a more specialized habitat
*The area under a dead tree, a portion of a drainage ditch, shade
under a tree, or other small areas are examples of microhabitats.
Even though microhabitats are small areas, they are complex and
a challenge to study.
Environmental conditions such as the amount of light, availability
of food, temperature, and moisture determines the variety of
organisms found in microhabitats.
Entomologists -scientists who study insects and their relatives.
A Berlese funnel trap is used to collect organisms living in leaves,
ground cover, and the soil. A bright, warm light is placed above
the funnel to encourage the organisms to move. Once they fall
into the trap, it is easier to observe the organisms and record
information.
Other tools useful for studying
microhabitats can include: hand lens,
insect trap, thermometer, digital camera,
ruler, tweezers, and hand shovel.
Berlese Funnel Trap
Unit 2 Lesson 4 Review/Study Guide
Environments and Organisms
 Biome -a large region of the world that is distinguished by
similar climate and organisms.
 There are 6 major land biomes of the world: tundra,
taiga, temperate forest, tropical rain forest, grassland, and
desert.
o Tundra :
 Located in an Arctic area of extremely cold temperature
 25 cm or less precipitation per year
 Receives the least amount of sunlight of all biomes
 Ground is frozen most of the time (permafrost)
 Poor soil quality
 Plants include: low growing grasses, shrubs, mosses
 Animals include: migratory birds, wolves, polar bears,
foxes, and caribou
 The Tundra has the least variety of plants and animals of
all 6 biomes.
o Taiga :
 Also called the coniferous forest
 Located just south of the Tundra
 25 cm – 125 cm of precipitation per year
 Poor soil quality
 Plants include: pine trees, spruce trees, fir trees and
hemlock
 Animals include: moose, elk, bears, beavers, deer, birds,
lynx and fox
o Temperate Forest :
 Also called the deciduous forest
 Located eastern and western regions of U.S., eastern
Europe, and western regions of Asia
 75 cm – 125 cm of precipitation per year
 Soil quality is rich with organic matter
 Plants include: oak trees, hickory trees, elm trees and
maple trees
 Animals include: deer, bears, snakes, rabbits, squirrels,
and variety of birds and insects
o Tropical Rain Forest :
 Located generally along the equator
 More than 200 cm of precipitation per year
 Receives the greatest amount of sunlight of all biomes
 Poor soil quality
 Plants include: giant trees, vines, and flowers
 Animals include: monkeys, squirrels, bats, snakes, birds,
rodents, and insects
 The Tropical Rain Forest has the greatest variety of plants
and animals of all 6 biomes.
o Grasslands:
 Also call Prairies, Pampas, and Savannahs
 Located throughout the world
 25 cm – 75cm precipitation per year
 Very rich soil
 Plants include: primarily grass
 Animals include: prairie dogs, mice, bison, foxes, zebras,
gazelles, hyenas, and wildebeests
o Desert :
 Located throughout the world
 Less than 25 cm of precipitation per year
 Receives a large amount of sunlight (though some deserts
are cold)
 Poor soil quality
 Plants include: cacti, small shrubs, and wildflowers
 Animals include: jackrabbits, rodents, bats, snakes,
toads, and insects
 Climograph –graph used to communicate the average
monthly temperature and precipitation in one graph.
o The bar graph represents the precipitation data using the
left y-axis
o The line graph represents the temperature data using the
right y-axis
 Below are 2 of the 6 example climographs you have in your
notes. Make sure you can interpret the amount of precipitation
and the temperature for any given month.
Tundra
Least variety of organisms
o The tundra has the least
variety of species due to
the very short growing
season, low precipitation,
and extremely harsh
temperatures.
Tropical Rain Forest
Greatest variety of organisms
o The tropical rain forest has
the greatest variety of
species due to the yearround growing season,
high precipitation, and
warm temperatures.
Texas is a very large state and contains a variety of
ecoregions.
Ecoregions -areas of similar environmental conditions such as
climate and landforms. Smaller than biomes, ecoregions are
home to distinct species and natural communities of
organisms.
o A diverse ecoregion will have a large numbers of individual
organisms and variety of species.
1 Which conclusion is best supported by the information provided in the Biome S
and Biome T tables?
A Both biomes receive the largest amount of precipitation in the warmer months.
B Biome T receives more solar radiation than Biome S.
C Biome T is less likely to have a wide variety of plants due to the climate.
D Biome S is most likely a desert, and Biome T is most likely grassland.
2
Which biome is likely to have the greatest variety of plants and animals?
A Tundra
B Desert
C Temperate forest
D Tropical rain forest
3 Which climograph would support the greatest variety of organisms?
A
C
B
D
Unit 2 Lesson 5 Review/Study Guide
Flow of Energy
The Sun is the ultimate source of energy. The Sun is where the
energy for ecosystems originates.
During photosynthesis, plants produce sugar (chemical energy)
that is stored for later use. Animals consume plants and use the
chemical energy obtained from sugar to go about their daily
activities.
Feeding relationships in an ecosystem:
Producers/plants (also called autotrophs): make their own
food using the energy of the sun
Consumers/animals (also called heterotrophs): get their
food by eating other organisms
- herbivores are consumers that eat producers (planteaters)
- carnivores are consumers that eat other consumers (meateaters)
- omnivores are organisms that feed on both producers and
consumers (plant and meat-eaters)
Decomposers (fungi/bacteria/earthworms, etc.) are
organisms that break down dead tissue, returning chemicals and
nutrients to the ground
Food chain -a simple model that shows the path of energy from
the Sun to the producer to a series of consumers in an
ecosystem.
The arrows in a food chain indicate the flow of energy.
Energy
Source
producer
1st -level
consumer
2nd -level
consumer
herbivore
carnivore
Food webs -a combination of overlapping food chains and also
represent the flow of energy.
Food webs are a more realistic model since they show many
possible feeding relationships.
Energy pyramid -used to show the amount of energy, or food
that is available to another organism at the next level of a food
chain.
It is a visual model reminding us that producers at the bottom of
the pyramid have greater energy available than the other
organisms.
10% Rule
Organisms use 90% of the energy they
obtain from their energy source during
life processes.
10
Units
For this reason, only about 10% of the
energy present at one feeding level is
passed to the next feeding level.
This is known as the 10% rule.
100
Units
1000
Units
10,000
Units
4 If there are 100,000 units of energy available from the kelp, approximately how much energy
is available for the sea otters?
A 1 unit
B 100 units
C 1000 units
D 10,000 units
Unit 2 Lesson 6 Review Study Guide
Biodiversity
Biodiversity -the variety of plants and animals in an ecosystem.
Sustainability -ecosystem’s health and ability to survive over a
long period of time.
Increase biodiversity = increase sustainability
Decrease biodiversity = decrease sustainability
 An increase in diversity of an ecosystem increases the
chance of survival of the organisms that the ecosystem or
habitat supports. Organisms have more “resources”.
Unit 2 Lesson 7 Review/Study Guide
Cycling of Matter
What would happen if trash were not collected and people did not
recycle any materials? The world would be a mess. We would
have more trash than living space, and we would be depleting
Earth’s natural resources. Eventually we could run out of the
resources we depend on to live. Think WALL-E.
Conservation -the wise use of natural resources.
Without conservation efforts, reserves of these resources will
quickly dwindle.
The ways to conserve are referred to as “The Three R’s”.
Reduce –to use less
Reuse –recovering items that would have been thrown away an
finding another use for them
Recycle – to convert into reusable material
Earth’s processes naturally recycle matter.
Water Cycle
Water falls to Earth as precipitation, collects on the surface and in
the ground, evaporates into the atmosphere, turns back into
liquid water as condensation (cloud formation), and then returns
as precipitation. The water is used over and over.
The Carbon Cycle
Several important processes are part of the carbon cycle:
Photosynthesis: plants take in carbon dioxide from the
environment (then release oxygen back into the atmosphere).
Respiration: most organisms get energy by combing oxygen
from the air with food in a process known as cellular respiration.
Carbon dioxide is released back into the environment as a waste
product.
Decomposition: decomposers (earthworms, isopods, bacteria,
etc.) break down the wastes or remains of other living things into
smaller molecules. The products of decomposition are simple
molecules, such as carbon dioxide and water.
The burning of fossil fuels and wood also release carbon dioxide
into the atmosphere.
The Nitrogen Cycle
The nitrogen cycle has many steps:
 Fish produce waste in the form of ammonia.
 There are bacteria that break down ammonia into nitrites.
 Different bacteria further break down nitrites into nitrates.
 Plants take in the nitrates to carry out life processes and
when the plants die, the nitrates are released in the
decomposition process.
This cycle happens over and over again. A very similar process
occurs in a terrestrial (land) environment.
1
As material in a compost bin decomposes, the organic
matter-
2
A
remains unchanged in form and composition.
B
will always degrade into toxic material.
C
is broken down into useful compounds such as
carbon.
D
eventually is completely destroyed.
Plants use nitrogen for —
A
decomposition.
B
photosynthesis.
C
producing glucose.
D
growth and productivity.
3
Nitrogen in the water is changed into a useable form
by —
A
plants.
B
animals.
C
bacteria.
D
producers.
Unit 2 Lesson 8 Review/Study Guide
Variations within Populations
Stimulus –a change that causes an adjustment by an organism
(anything an organism can sense).
 External stimulus – comes from outside the body(use of the
five senses)
 Internal stimuli – comes from inside the body (hunger,
thirst, pain, etc.)
Response –a change in behavior, physiology, or appearance of
an organism (a reaction).
Innate behavior – behavior an organism is born with
(rattlesnake rattling tail, young offspring nursing, young sea
turtles heading towards ocean, baby birds hatching from their
eggs, etc.)
 Migration –seasonal movement of animals from one place to
another.
 Hibernation –a deep sleep in which body systems reduce to
minimal levels.
Learned behavior –behaviors that an organism learns from
observation or direct experience (prey learning to stay away from
rattlesnake, young offspring learning to hunt, teaching a dog a
trick.)
1
2
Roots grow downward in the soil in response to -
A
the external stimuli gravity .
B
the internal stimuli gravity.
C
the external stimuli the sun.
D
the internal stimuli the sun.
Thirst is -
A
a learned behavior.
B
an internal stimuli.
C
a form of migration.
D
a form of hibernation.
Unit 2 Lesson 9 Review/Study Guide
Many of today’s ideas about evolution are based on the work of
Charles Darwin. In the 1850's, Darwin described how organisms
might change over time (adapt). Most of these ideas came from
observations Darwin made during the five years he worked as a
naturalist on the research ship H.M.S. Beagle.
A part of his journey, Darwin observed and studied 13 different
species of finches living on the Galapagos Islands.
As a result of his studies, he discovered that when species
reproduce, the survivors will pass on favorable traits to their
offspring. If an offspring did not receive the favorable trait, the
offspring will likely die before passing on an unfavorable trait.
Natural selection -process by which organisms change over
time as those with traits best suited to an environment pass their
traits to the next generation
Adaptation -an activity or action that helps an organism survive
its environment or surroundings.
Examples of adaptations can include:
 Spiny/waxy leaves of a plant to prevent water loss
 fur color of an animal to blend in to its environment
(camouflage)
 physical structure of bird beaks to better obtain food
 hard shell of a crab to protect it from its predators, etc.
1
2
Several years of drought affect a population of plants in
southwest Texas. Which of the following characteristics
would you expect to see more frequently in the plants over
the next several generations?
A
Abundant broad leaves
B
Waxy coating on leaves
C
Flowers blooming regularly
D
Tall, narrow stems
A population of birds walks along the shores of a swampy
area eating small crabs. Climactic changes cause the water
level in the area to increase. Which genetic variation in the
bird population will be at an advantage leading to greater
survival in the area?
A
Longer legs for wading
B
A thicker coat of feathers
C
Shorter, stronger beaks
D
Sharper talons on the feet
3
Mudskippers are a species of fish which, over thousands of
generations, have developed adaptations that allow them
not only to survive outside of the water, but to actually
travel from one water source to another. What
environmental condition most likely led to these
adaptations?
A
Lower temperatures
B
Frequent droughts
C
Larger predators
D
Increased precipitation