- Plants have three main organ systems - roots, stems, and leaves - that carry out key functions like water and nutrient absorption, photosynthesis, and providing structure and support. - Within plants, chloroplasts use energy from sunlight to produce glucose through photosynthesis. Plants get their energy from glucose. Animals then obtain energy by eating plants or other animals that eat plants. - Metabolism refers to the chemical reactions in organisms that break down glucose to produce energy. This energy transfer between organisms through food webs and food chains drives ecosystem function.

2. Plants have three organ systems
• Roots: absorb water and mineral,
and anchors plants to the ground
• Stem: supports leaves and branches
• Xylem and Phloem run like a
plumbing system through the
stem and connects roots to the
leaves
• Leaves: main organs of plants that
conduct photosynthesis:
• intercepts sunlight, captures
carbon dioxide, and stores
energy in the form of glucose
• releases oxygen into the air in a
process called transpiration

3. • The chloroplast in plants use the
energy in sunlight to make a
sugar called glucose. Plants
energy from glucose.
• Animals get energy from eating
plants or eating animals that eat
plants.
• The process by which cells break
down glucose (a sugar) to
produce energy

5. • Population: a group of organisms that belong to the same species
• Species: a group of organisms that are capable of interbreeding and
producing fertile offspring

6. webs, arrows always
● The feeding relationships in an ecosystem can be shown in a Energy flows in one direction through an ecosystem. Green plants
point from the organism
food web, which consists of many interconnected food chains. convert the sun’s energy to food energy (potential chemical energy).
that is consumed to the
● All food chains and food webs begin with producers. consumer. Arrows show the plants are the next step. These animals are eaten
Animals that eat
by other animals. At each level in a food chain, consumers convert
the flow of matter and
● Energy moves through ecosystems in food chains and food webs energy. food energy to mechanical energy, which is used for activities
some
every time an organism eats another organism. such as running and breathing. However, much of the energy stored in
●
• An interactive systemRemember! includes the physical environment
Energy cannot be recycled.
that food is used for metabolic processes, such as maintaining a constant
body temperature.
and the organismsMetabolismWeb to all theretransferredabout 10 percent ofInthe energy atfor instance, nearly half of
thatrefers
chemical live
theFood reactions
Partial African Grassland
In fact, only
is to the next level. mammals,
any level in a food chain
that take place in an the energy obtained from food is lost to the environment as heat. This
organism. is why there are usually only four levels in a food chain. Only rarely
Scavengers is there enough energy available to support a fifth level. An energy
Vultures pyramid shows the relative amount of energy available at each level.
Carnivores
Lions Cheetahs Energy Pyramid
Herbivores
Carnivores that eat carnivores
Zebras Baboons Impalas Giraffes
Producers
Grasses Acacia trees Carnivores that eat herbivores
Decomposers
Fungi Bacteria
Herbivores
This grassland food web is made up of producers, consumers (herbivores,
carnivores, and scavengers), and decomposers. Scavengers such as
vultures feed on the remains of dead animals. Decomposers such as Producers
bacteria and fungi decompose dead organisms and their wastes.
45 An energy pyramid shows the energy stored at each trophic (feeding) level in an ecosystem.

7. Organisms don’t live in isolation. All living things depend on their
environment and other organisms for survival. The environment has
an effect on individual organisms and on populations of organisms.
You need to be able to show that you know this relationship.
Remember!
A population of organisms—what’s that?
• Natural Selection: Individual organisms have differences or
A population is a group of organisms that belong to the same species,
A species is a group of
organisms that are
variations-factors such as environment, food, or space can make one
live in the same area, and breed with other individuals in the group.
For example, there are populations of humans, populations of sharks,
capable of interbreeding
and producing fertile
populations of oak trees, and populations of mosquitoes.
variation more favorable than another. Over time, the population
offspring.
I understand how the environment affects individual organisms, favorable variations.
will have individuals with more
but how does the environment affect entire populations?
• Evolution: evolution occurs when the genetic make-up of a
Good question! Individual organisms have differences, or variations.
Factors in the environment such as the amount of food or space
population changes over time due to natural selection
can make one variation more favorable than another. Over time the
population will have more individuals with the favorable variation.
This process is called natural selection.
D you know?
id
A single swarm of R ocky
Mountain locusts was
estimated to contain 1 2.5
trillion insects. That’s a
large population!
©PhotoDisc ©Paul A. Souders/CORBIS
These bears belong to the same species, but they have different fur colors
because of genetic variations. The darker fur color may be more favorable
in certain environments, and the lighter fur color may be more favorable in
others.
37