Content Review for 7th Grade Science
7-2.1, 2.2 Cell Structures and Functions
It is essential for students to know
 the cell is the smallest unit of life
 cells vary in size, but contain many of the same major parts
 the cell membrane is the outside covering of a cell. It controls what comes in and out of a cell
 the cytoplasm is the gel-like fluid inside of a cell. The other organelles are embedded in the cytoplasm
 the nucleus contains DNA and is the control center of the cell
 the vacuole(s) act as storage centers
 the chloroplasts are the food-making structures of a plant cell
 the mitochondria use oxygen to release energy from food. It is sometimes called the “powerhouse” of the cell
 the cell wall provides extra support and shape for plant cells. It is made mostly of cellulose
It is not essential that students know endoplasmic reticulum, Golgi bodies, lysosomes, or ribosomes.
It is essential for students to classify the major structural differences between a plant and an animal cell include .

Plant cells have a cell wall, but animal cells do not. Cell walls provide support and give shape to plants.

Plant cells have chloroplasts, but animal cells do not. Chloroplasts enable plants to perform photosynthesis to make food.

Plants cells usually have one or more large vacuole(s), while animal cells have smaller vacuoles, if any are present. Large
vacuoles help provide shape and allow the plant to store water and food for future use.
It is not essential for students to know other organelles in plant and animal cells or to know the chemical processes that occur within
the cell parts.
Key Words: prokaryotes, eukaryotes, nucleus, cell membrane, cytoplasm, organelles, ribosomes, endoplasmic reticulum, Golgi
apparatus, lysosomes, mitochondria, vacuoles, autotroph, heterotroph
Cell Component
Function
Plant Cell
Animal Cell
Nucleus
Controls all cell activities;
Present
Present
contains DNA (cell’s heredity
information)
Chromosomes
Present
Present
Ribosomes
Present
Present
Cell Membrane
Present
Present
Cell Wall
Present
Absent
Cytoplasm
Present
Present
Endoplasmic Reticulum
Present
Present
Golgi Apparatus
Present
Present
Lysosomes
Present
Present
Mitochondria
Present
Present
Chloroplasts
Present
Absent
Vacuoles
Present
Present
Nucleolus
Present
Present
*** Prokaryotes do not have a
*** Eukaryotes have a nucleus
nucleus (bacteria)
(plant / animal cell)
1. Which cell structure found in plant and animal cells contains the genetic material and the information to make proteins?
2. What structure in plant cells gives them a rectangular shape?
3. Which structures in plant and animal cells are vital for the breakdown of food particles, wastes, and cell parts that no
longer function?
4. What structure in plant cells converts carbon dioxide and water into oxygen and glucose?
5. Which cell structure is found in plant and animal cells and controls what can come into or leave a cell?
6. Which organelles play a role in the making of proteins?
7. All cells need energy to function. Which organelle in animal and plant cells is responsible for making energy in these
cells?
7-2.3 Bacteria and Protists
It is essential that students be able to classify bacteria by their shape and protists (euglena, paramecium, amoeba), by the way they
move and gather food.
Students should know that there are three basic bacterial shapes.
Round
Round bacteria are referred to as cocci 
Rod shaped
Rod shaped bacteria are known as bacilli
Spiral
Spiral shaped bacteria are corkscrew shaped are known as spirilla
Protists are organisms that are classified into the kingdom Protista. Although there is a lot of variety within the protists, they do share
some common characteristics.
All protists have

a nucleus with a nuclear membrane

are usually one-celled.

live in moist environments
Protists are grouped by the way they move and obtain food:

Protists with Pseudopods (for example the amoeba) These protists move by extending their bodies forward and then
pulling the rest of their bodies forward as well The finger-like structures that they project forward are called pseudopods
(false foot). The pseudopods are also used to trap food.

Protists with Cilia (for example the paramecium) these protists move by beating tiny hair-like structures called cilia.. The
cilia act as tiny oars that allow the protist to move through its watery environment. The cilia also beat and help to capture
food

Protists with Flagella (for example the Euglena) These protists move pulling themselves with long whip like structure
called flagella. These protists can have one or more flagella that help them move. The euglena is unique in that it has
characteristics of both a plant and an animal, it contains chloroplasts that photosynthesize and also can consume other
organisms as well.
Key Words: bacteria, bacilli, cocci, spirilla, flagella, protists, Euglena, paramecium, cilia, pseudopods, amoeba
Bacilli Bacteria
Cocci Bacteria
Spirilla Bacteria
Bacillus anthracis
Streptococcus pneumonia
Treponema pallidum
Bacillus bacteria
Cocci bacteria
Spirilla bacteria
Causes anthrax
Causes pneumonia
Causes syphilis
Rod shaped
Round shaped
Spiral shaped
Euglena (single celled protest)
Paramecium (single celled protest)
Plant like protist that moves with a
Animal like protist that moves w/ cilia
flagellum; looks green; makes own food
(tiny hair-like structures) which help
w/ chloroplasts; live in fresh water;
propel it and sweep food toward its food
contractile vacuole pumps out excess
passageway
water
1. What structure in bacteria gives them their shape?
2. What characteristic makes single-cell protists different from bacteria?
3. What structure in paramecium allows for movement and food capture?
4. How are bacteria classified?
7-2.4 Cell Process and Survival
It is essential that students be able to understand
Amoeba (single celled protest)
Moves with a pseudopod (false foot) that
stretches out from the cell; uses
pseudopod to move and catch food;
pseudopod surrounds food and forms food
vacuole
Cellular processes for survival
Photosynthesis
Respiration
Elimination
Mitosis
The life cycle begins with photosynthesis within a plant cell. The plant, uses the energy from
sunlight, carbon dioxide, and water, to make food. The plant cell then releases oxygen as waste.
Once the “food” is formed it is either used by the plant or consumed by an animal. This food is
broken down in the plant or animal’s cell through a process called respiration.
Breaks “food” into carbon dioxide, water, and energy. Carbon dioxide and water are the waste
products of respiration. The cell uses the energy to build, repair, and reproduce cells.
Rids the cells of waste products that would be toxic to the cell. Molecules move from a crowded area
to a less crowded area (diffusion), as waste molecules accumulate in a cell, the waste will move out
of the cell and be eliminated.
Cell reproduction is called mitosis. Mitosis enables a cell to make an exact copy of it. Mitosis is a
process of cell division, which results in the production of two daughter cells from a single parent
cell. The daughter cells are identical to one another and to the original parent cell. Mitosis is needed
for growth, replacement, and asexual reproduction.
It is not necessary for students to know the stages of mitosis
Key Words: photosynthesis, reactants, products, ATP, cellular respiration, interphase, mitosis, cytokinesis, passive transport, active
transport
Photosynthesis
Cellular Respiration
provides plants with the glucose needed to make energy and
Plant and animal cells use ATP for energy. Mitochondria
provides animals with oxygen
convert glucose to ATP. ATP is made through a process known
as cellular respiration.
radiant energy + 6 (CO2) + 6(H20) 
C6H12O6 + 6(O2)
C6H12O6 + 6(O2)  6(CO2) + 6(H2O) + ATP
CELL CYCLE:
(1) Interphase: cell carries out normal activities, growing in size; cells components are copied near the end of interphase
(2) Mitosis: nuclear division takes place in 4 phases: PROPHASE, METAPHASE, ANAPHASE, TELOPHASE; copied pairs of
chromosomes separate
(3) Cytokinesis: cytoplasm divides into two cells and the separated chromosomes become bound into a new nucleus in each cell;
nuclear membrane and cell membrane produced
1. Which cell structure found in plant and animal cells enables them to make ATP?
2. The producs of photosynthesis are the same as the reactants in cellular respiration? What are these molecules?
3. Cells get rid of wastes in two ways. Which way requires the cell to use ATP?
4. In which part of the cell cycle are two new cells formed?
7-2.5 Genes and Heredity
It is essential that students know:

Genes are usually known as the physical unit of heredity. Genes are formed from DNA, located on the chromosomes and
are responsible for the inherited characteristics that distinguish one individual from another. Each human individual has an
estimated 30,000 separate genes.

Chromosomes are the self-replicating genetic structures of cells.

Inherited traits are those that are passed from parent to offspring. Examples of inherited traits are eye color, eye shape, hair
type, or face shape.

Some of the traits passed from parent to offspring are dominant. A dominant trait is one that will always be expressed.
Alleles for dominant traits are represented by a capital letter.

Some of the traits are recessive. A recessive trait is one that will only be expressed if two recessive traits have been passed.
In the presence of a dominant trait, the recessive trait will not appear. Alleles for recessive traits are represented by a
lowercase letter.

The phenotype of an organism encompasses its physical and behavioral characteristics. For example, eye color, height, or
skin color, all constitute the phenotype of an individual. In other words, the phenotype refers to the physical characteristics
of an individual.

The genotype consists of the genetic makeup of an organism. It represents the collection of all the genes found on the
chromosomes in the nucleus of each cell. These genes are used as a "blueprint" or set of instructions for building and
maintaining a living creature.
Mechanisms of Inheritance
Biological information can be passed on from one generation to the next. Each gene is copied and
then the copy is transferred to the new cell or organism as it reproduces and duplicates itself:

Reproduction is a basic and fundamental process common to all forms of life on earth.

In this process organisms and cells produce new copies of themselves by following the instructions and blueprints they all
carry in the genetic code.

During reproduction these instructions and blueprints, in the form of biological information, are copied and then passed on
from one generation to the next. This is inheritance. The offspring receives one gene from each parent.

Cellular life depends on the ability of cells to grow, copy their biological information, and then divide into two new cells,
ensuring that each new cell receives a complete copy of all the information it needs. This is cell division.
It is not essential for students to know the detailed workings of DNA, the terms cytosine, guanine, adenine, or thymine or RNA.
Key Words: chromosomes, genotype, phenotype, heredity, inherited traits, genes, dominant trait, recessive trait
7-2.6 Using Punnett Squares
It is essential that students be able to use a Punnett square to predict the inheritance of monohybrid traits.
A monohybrid inheritance is the inheritance of a single characteristic.

The cross that involves one pair of contrasting traits

For example, crossing a tall (Tt) plant a short (tt) plant is a monohybrid cross

Every new cell has received one gene from each parent

For example a cell with Tt genotype has received a gene for tall height dominance (T) from one parent and a recessive gene
for short height from the other parent (t).

Each parent has two genes and the probability that the offspring receive one or the other gene is determined by a Punnett
square.
Female Parent
Male Parent
Offspring: Tt, Tt, tt, tt
7-2.7 Inherited and Acquired Traits
It is essential for students to know that some characteristics that organisms have are inherited from their parents and some can be
influenced by environmental factors.
An inherited trait is a particular genetically determined characteristic or quality that distinguishes an organism from other organisms.


Inherited traits are passed on from generation to generation when chromosomes carrying genes are passed from parent to
offspring in sex cells.
Some inherited traits are dominant, some are recessive, and some are neither.

Examples of inherited traits in humans include color blindness, baldness, blood type, and skin color, the ability to taste certain
substances, or free or attached ear lobes.
Any characteristic or behavior that cannot be attributed to a genetic value or genes of the individual is said to be a result of
environmental factors. Examples of environmental factors that can affect traits of organisms include temperature, diet, medical care,
or living conditions. Environment determines the phenotypic pattern of expression.
7-3.1 Levels of Organization
It is essential for students to know that the human body is divided into specific levels of organization and that these levels are what
make the human body a complex organism. The levels of organization, from the simplest structure to the most complex are:
Cells
The basic units of structure and function within the human body. Though all cells perform the processes that keep humans
alive, they also have specialized functions as well. Examples are nerve cells, blood cells, and bone cells.
Tissues
Organs
Systems
A group of specialized cells that work together to perform the same function. There are four basic types of tissue in
the human body:
 Nerve tissue—carries impulses back and forth to the brain from the body
 Muscle tissue—contracts and shortens, making body parts move
 Epithelial tissue—covers the surfaces of the body, inside and outside
 Connective tissue—connects all parts of the body and provides support
Blood, an example of a tissue, is composed of several types of cells, including red blood cells, white blood cells,
platelets, and plasma that function to transport materials from one part of the body to another.
Are comprised of two or more different types of tissues that function together to perform a specific function. The
task is generally more complex than that of the tissue. For example, the heart is made of muscle and connective
tissues which function to pump blood throughout the body.
A group of two or more organs that work together to perform a specific function for the human body. All of the
different organ systems work together and depend on one another. There are eleven different organ systems in the
human body: circulatory, digestive, endocrine, excretory (urinary), immune, integumentary (skin), muscular,
nervous, reproductive, respiratory, and skeletal.
It is not essential for students to know the major tenets of the cell theory or explain the process of cell differentiation.
7-3.2 Organs and Organ Systems
It is essential for students to know the major organs of the human body and be able to list their functions within their identified body
system. The major organs and their functions that students should be able to identify are:
Major Organs
Function (s)
Heart
Blood vessels (arteries, capillaries
and veins)
Nose
Causes blood to flow through the body by it pumping action
Tubes that carry blood throughout the entire body
System
Circulatory
Respiratory
Trachea
Bronchi
Digestive
Diaphragm
Mouth
Esophagus
Stomach
Small intestines
Large intestines
Rectum and anus
Major Organs
Collects air from the environment and moistens and heats the air
before it enters the trachea
The windpipe; moves air from the nose to the lungs
Tubes that move air from the trachea to the lungs; one bronchus leads
to each lung; part of each bronchus is outside the lung and part is
inside.
The dome-shaped muscle that aides in the breathing process
Begins to break down food into smaller pieces through mechanical
digestion; saliva in the mouth starts the process of chemical digestion
The transport tube that carries chewed food to the stomach
Continues the process of mechanical digestion; secretes enzymes that
perform some chemical digestion of food
The organ where most of the chemical digestion of food takes place;
nutrients from food are also absorbed through the small intestines
The organ where water is absorbed from the food and taken into the
bloodstream; prepares the remaining food material for elimination
from the body
The rectum is a short tube that stores solid waste until it is eliminated
from the body through the anus.
Function (s)
System
Digestive continued
Liver
An ancillary organ of the digestive system that produces bile which is
used by the body to break up fat particles.
Pancreas
Gallbladder
Excretory (Urinary)
Kidneys
Ureters
Bladder
Nervous
Urethra
Brain
Spinal cord
Peripheral nerves
Muscular
Skeletal muscles
Smooth muscles
Skeletal
Cardiac muscles
Bones
An ancillary organ to the digestive system that functions to produce
enzymes that help break down starches, proteins, and fats in the small
intestine.
An ancillary organ to the digestive system that functions to store bile
produced by the liver.
The two kidneys function to get rid of urea , excess water, and some
other waste materials which are eliminated in urine
Tubes which connect each kidney to the bladder
A saclike muscular organ which stores urine until it is released from
the body
Tube through which urine passes before it is removed from the body.
An organ of the central nervous system which has three distinct parts
that all serve to control and coordinate the body’s activities. The
cerebrum controls thoughts, voluntary actions, and the sensations
related to the five senses. The cerebellum helps with balance and
coordination. The brain stem is located at the base of the brain and
controls vital and involuntary processes, for example, breathing, the
beating of the heart, and digestion.
A bundle of nerves that begins at the brain stem and continues down
the center of the back. It connects with nerves outside the central
nervous system and controls reflexes and directs sensations to the
brain.
A network of nerves that branch out from the spinal cord and connect
to the rest of the body. The peripheral nervous system is divided into
groups called the motor and sensory nervous systems.
Voluntary muscles that are attached to bones and provide the force
needed to move your bones
Involuntary muscles that control many types of movement in the body
(i.e, digestion)
Involuntary muscle that forms the heart
Provide shape and support for the body and protection for many
organs and structures; some bones produce blood cells; some store
minerals
Major Organs
Function (s)
Skin
Covers the body and prevents the loss of water; it protects the body
from infection and injury; it helps to regulate body temperature, get
rid of wastes (sweat), receive information from the environment and
produce vitamin D.
System
Integumentary
It is not essential for students to know the major organs of the reproductive system, immune system, endocrine system.
7-3.3 Human Body Systems
It is essential for students to know that the different organs systems in the human body function together and depend on one another
for the human body to function successfully, even though each system performs its own unique function. Of the eleven systems in the
body, students should know how the following systems work together:
Nervous System
The main role of the nervous system is to relay electrical signals through the body. The nervous
system directs behavior and movement and, along with the endocrine system, controls physiological
processes, for example digestion, circulation, or movement.
The body cells need oxygen to function. Taking in oxygen and transporting it to cells are the jobs of the respiratory and circulator
systems.
Circulatory System
The main role of the circulatory system is to transport nutrients, gases (for example oxygen and
carbon dioxide), hormones, and wastes through the body.
Respiratory System
The main role of the respiratory system is to provide gas exchange between the blood and the
environment. Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide
is expelled from the body.
The circulatory and digestive systems work together to ensure that nutrients made available by digestion get to the cells of the body.
The digestive and excretory systems work together to take in materials your body needs and gets rid of wastes.
Digestive System
The main roles of the digestive system are to breakdown and absorb nutrients that are necessary for
growth and maintenance.
Excretory System
The main role of the excretory system is to filter out cellular wastes, toxins and excess water or
nutrients from the circulatory system.
The muscular and skeletal systems work together to help the body move.
Muscular System
The main role of the muscular system is to provide movement. Muscles work in pairs to move limbs
and provide the organism with mobility. Muscles also control the movement of materials through
some organs, for example the stomach and intestine, and the heart and circulatory system.
Skeletal System
The main role of the skeletal system is to provide support for the body, to protect delicate internal
organs and to provide attachment sites for the organs.
It is not essential for students to know the functions of the reproductive system, immune system, endocrine system, or
integumentary system. These systems will be studied in Health.
It is also not essential for students to know the chemical processes within each system.
7-3.4 Infectious Disease
It is essential for students to know that a disease is a condition that does not allow the body to function normally. Diseases can affect
either an individual organ or an entire body system. Diseases are divided into two groups—infectious and noninfectious.
Tiny organisms called pathogens cause infectious diseases. These pathogens can be bacteria, viruses, fungi, or protists. These
pathogens can come from another person, a contaminated object, an animal bite, or the environment. The immune system is
responsible for distinguishing between the different kinds of pathogens and reacting to each according to its type. Once a pathogen
enters has entered the body, it works by damaging individual cells within the organs or in some cases attacks an entire body system.
Some examples that students should know are:
Colds
A common cold is an illness caused by a virus infection located in the respiratory system. Cold viruses can only
reproduce when they are inside living cells. When located on an environmental surface (for example a doorknob
or drinking glass), cold viruses cannot reproduce. However, they are still infectious and can be transported from
the environmental surface to the nose or mouth.
Flu
(Influenza)
Influenza, commonly known as "the flu," is a highly contagious viral infection of the respiratory system.
Influenza typically causes fever, muscle aches, and a more severe cough than the common cold and usually last
longer.
Strep throat
(bacterial) Strep throat is a contagious disease caused by infection with bacteria. Strep throat symptoms include
fever, pain, redness, and swelling of the throat and tonsils. Strep throat may produce mild or severe symptoms.
Athlete’s foot
Athlete’s foot is a common fungal infection of the skin of the feet. The fungus is contracted from public
environments and then grows in the warm and moist environment usually between the toes, and can be difficult to get rid of.
AIDS
Acquired immunodeficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV). This virus attacks
the cells in the immune system making the organism unable to fight off other pathogens that may attack the body.
Noninfectious diseases are diseases that are not caused by pathogens in the body and are not spread from organism to organism. These
diseases are either caused by cardiovascular disease, allergies, diabetes, and cancer are examples of noninfectious diseases.
Some noninfectious diseases that students should know are:
Diabetes
Diabetes is a disease that results in the glucose, or sugar, level of the blood being higher than the
normal range. It is caused by a person’s inability to either produce or use properly a natural chemical
produced in the body called insulin. The higher level of blood sugar results many disorders of the
body, for example it increases problems with circulation of blood, and it can lead to kidney disease
and heart disease, or cause vision problems.
Asthma
(Involves the respiratory system) Asthma is a disease that affects the lungs and the airways that
deliver air to the lungs. It causes periodic attacks of wheezing and difficult breathing. An asthma
attack occurs when the airways become inflamed in response to a trigger, such as dust, mold, pets,
exercise, or cold weather. However, some attacks start for no apparent reason
Parkinson’s disease
Parkinson's disease occurs when certain nerve cells in the brain die or become damaged. Parkinson's
disease does not affect everyone the same way. In some people the disease develops quickly, in
others it does not. Although some people become severely disabled, others experience only minor
motor disruptions. Tremor is the major symptom for some people, while for others tremor is only a
minor complaint and different symptoms are more troublesome. At present, there is no cure for
Parkinson's disease.
Skin Cancer
Skin cancer is a disease in which cancer cells are found in the outer layers of your skin. Your skin
protects your body against heat, light, infection, and injury. It also stores water, fat, and vitamin D.
Sunburn and UV light can damage your skin, and this damage can lead to skin cancer. However,
there are other determining factors, including heredity and the environment.
It is not essential for students to know how the immune system specifically responds to different pathogens (for example T-cells and B
cells) or to go into depth regarding other diseases of the human body.
7-4.1 Ecosystems
It is essential for students to know that the ecosystems are divided into specific levels of organization and that these levels are what
make the ecosystem complex. The levels of organization, from the simplest to the most complex are:
Species
Species are the different kinds of organisms found on Earth. A more exact definition of
species is a group of similar organisms that can reproduce with each other.
Populations
A population comprises all the individuals of a given species in a specific area or region at a certain time.
The location where a population obtains food, water, shelter and other things needed in order to survive
is called its habitat. The particular role that the population serves in its environment is called its niche.
Communities
Community refers to all the different populations in a specific area or region at a certain time. Its
structure involves many types of interactions among species. Some of these involve the gathering and use
of food, space, or other environmental resources. Others involve nutrient cycling through all members of
the community.
Ecosystems
Ecosystems are dynamic units composed of the community and the abiotic environment, including water,
sunlight, oxygen, temperature and soil.
Biomes
Biomes are the largest recognizable assemblage of animals and plants on Earth and are determined
mainly by climate.
It is not essential for students to know the specific interrelationships among organisms
7-4.2 Energy Flow (Food Chains, Food Webs, Energy Pyramids)
It is essential for students to know organisms have energy roles that they serve in their environments. Each role is determined by how
the organism obtains its energy and how they interact with other organisms in the environment. These roles can be as a producer,
consumer or decomposer. The flow of energy can be represented using the following diagrams:
Food chain
Uses pictures or words and arrows to show the movement of energy through the trophic levels of
organisms. The trophic level of an organism indicates the position that the organism occupies in the food
chain—what it eats and what eats it. The levels are numbered according to how far the particular
organism is along the chain from the primary producer at Level 1, to herbivores (Level 2), to predators
(Level 3), to carnivores or top carnivores (Levels 4 or 5).
Food web
Describes the organisms found in interconnecting food chains using pictures or words and arrows. Food
webs describe the complex patterns of energy flow in an ecosystem by modeling who consumes whom or
what.
Energy pyramid
Shows the amount of energy that moves from one trophic level to another in a food chain. The most
energy is available at the producer level of the pyramid. Energy availability decreases as it moves up the
energy pyramid.
It is not essential for students to know how to calculate the amount of energy transferred or lost from one level to another level.
Students do not need to know the roles that organisms play in the geochemical cycles (including the
cycles of carbon, nitrogen, and water). It is also not essential for students to know the relationships
among organisms (including predation, competition, parasitism, mutualism, and commensalism) as
these topics will be discussed in high school biology.
7-4.3 Changes in the Environment Due to Natural Hazards, Changes in Populations, and Limiting Factors
It is essential for students to know there are various factors that can change the environment. Students should be able to construct
cause and effect models for each factor and how it affects the environment.
Changes in the environment can occur due to natural hazards.
Landslides
Landslides are rock, earth, or debris flows on slopes due to gravity. They can occur on any terrain given the
right conditions of soil, moisture, and the angle of slope. Landslides can be caused by rains, floods, earthquakes,
and other natural causes, as well as, human-made causes such as excessive development or clear-cutting for
lumber. Examples of ways that landslides can effect the environment are blocking roads, damaging or
destroying homes, destroying habitats, or disrupting power lines.
Wildfires
Fire is a natural event in most forest ecosystems. Fires can be beneficial to the ecosystem and are an essential
component in the life cycle of some trees. Generally, fires are neither good nor bad. They occur naturally
through lightning strikes or when humans start them accidentally or intentionally. Examples of the effects of
wildfires on the environment are increased air pollution, habitat destruction, or destroying homes or property.
Floods
A flood is an unusually high water stage in which water overflows its natural or artificial banks onto normally
dry land. There are two basic types of floods. In a regular river flood, water slowly climbs over the edges of a
river. The more dangerous type, a flash flood, occurs when a wall of water quickly sweeps over an area. A
number of factors can contribute to the cause of a flood, including:

heavy, intense rainfall

over-saturated soil, when the ground can't hold anymore water.

high river, stream or reservoir levels caused by unusually large amounts of rain

urbanization, or lots of buildings and parking lots
Examples of the effects of floods on the environment include damaging property, endangering humans and
animals, or causing soil erosion and deposition of sediment.
Changes in the environment can occur due to changes in populations. Changes in populations can occur when new members enter a
population or when members leave a population. These changes can have an effect on the amount of resources available in the
environment. This can lead to competition for food, water, space, or shelter.
Births and Deaths
New births are the main way that organisms are added to a population. The number of
births in a population during a certain amount of time is called the birth rate. Deaths are
the main way that organisms leave a population. The number of deaths in a population
during a certain amount of time is called the death rate.
Immigration & Emigration
The size of the population can change when members move into or out of the population.
Immigration is when organisms move in from another environment. When part of the
population leaves the environment, this is known as emigration.
Changes in the environment can occur due to limiting factors.
Climate
Climate refers to the temperature and amount of rainfall in a particular environment. Changes in
temperature and the amount of rainfall from the norm can change an environment which will have an
effect on the populations in the area.
Availability of food
Availability of water,
space, and shelter
Organisms require a certain amount of food to survive. When the amount of food available in a
given area is less than what the various populations need, food becomes a limiting factor.
Plants and animals need space for various reasons. Plants need space in order to, grow, and obtain
the necessary nutrients from the soil. Animals need space in order to find food and shelter. When the
amount of space in an environment cannot support the populations present, space becomes a limiting
factor.
Carrying capacity
The maximum number of organisms an environment can support
It is not essential for students to know how the interrelationships of organisms create stability in an environment or how human
activities affect the environments.
7-4.4 Soil Quality
It is essential for students to know that soil quality is based on properties that can be observed such as soil profile, composition,
texture, or particle size, as well as measured, such as permeability and pH.
Observable properties:
Soil profile:
Soils form in layers, or horizons, and all the layers make up the soil profile. A mature soil profile consists of
three layers – topsoil, subsoil, and parent material above bedrock. Topsoil that is nutrient rich, containing a
mixture of humus, clay, and minerals is most suitable for plant growth. Most animals live in the topsoil
horizon.
Composition:
Soil is a mixture of rock particles, minerals, decayed organic material, air, and water. The decayed organic
matter in soil is humus. The sand, silt, and clay portion of soil comes from weathered bedrock material. The
combination of these materials in soil affects the type of plants that can grow in it or animals that can live in it.
Texture:
Soil texture depends on the size of individual soil particles and is determined by the relative proportions of
particle sizes that make up the soil. Texture names may include loam, sandy clay loam, silt loam, or clay
depending upon the percent of sand, silt, and clay in the soil sample.
Particle size:
Soil particles are classified by size ranging from coarse sand to very fine sand to silt, and finally to the smallest
particle, clay. Soil particles that are larger than 2mm are called gravel.
Measurable properties:
Permeability:
Soil particles have open spaces between them that let water flow through. How freely that water flows is the
permeability of the soil. The closer the particles pack together because of particle size, the less permeable the
soil is. Measuring permeability involves calculating the rate of drainage.
pH:
Soils can be basic or acidic and usually measure 4-10 on the pH scale. Indicators can be used to measure the
pH of soils. Most plants grow best in soils with a pH of between 5 and 7. Lime is a kind of fertilizer and can
be added to make the soil more basic.
Students should know that soil is one of the most valuable abiotic factors in an ecosystem because everything that lives on land
depends directly or indirectly on soil. Soil formation takes a long time, so the quality of soil that is in an ecosystem helps to maintain
that ecosystem. Should soil quality change in any of its properties, the ecosystem and life in it could also change. An example of this
change is evident because Earth is losing about 7% of its topsoil each decade, and the result is an increase in global deserts.
Ecosystems change as soil quality changes.
Students should understand this explain indicator as cause and effect; the soil quality properties effect the characteristics of an
ecosystem.
It is not essential for students to measure soil temperature, moisture content, conservation methods, or specific grain size for soil
particle classification.
7-4.5 Location and Movement of Water
It is essential for students to know that the when water falls to Earth, some water soaks into the ground becoming part of
groundwater and gravity causes some of it to flow downhill instead of soaking into the ground; this is called runoff.
Groundwater:
is water that soaks into the ground. Soil and rock that allow the water to pass through is called permeable. The
water enters into the zone of aeration, which is unsaturated. Groundwater will keep moving deeper into Earth
until it reaches a layer of rock that is not permeable. The area where the water has filled all the space in the
soil is called the zone of saturation; the top of this zone is the water table. Groundwater can also flow slowly
through the underground rock sometimes dissolving it away forming tunnels, caves, and caverns.
Surface-water:
is runoff that has not soaked into the ground. As runoff travels downhill, it forms the water in streams and
rivers. An area that is drained by a river and all the streams that empty into it, the tributaries, is called a
drainage basin or watershed. A divide is the high ground between two drainage basins. By studying a map
that contains rivers and marking all the tributaries of that river, the watershed area can be identified.
Students should understand that the availability of water as groundwater or surface-water is important to the ecosystems in that area.

Flowing water can erode the land in one location and deposit the sediments in another.

The floodplain of a river may deposit sediment after heavy rains enriching the area with new soil needed for growing vegetation.
This new soil is nutrient rich. Crops or natural vegetation grow well in it.

The drainage basin provides the needed water for animal life also.

Deltas may form where the river ends its journey into a still body of water like a lake or the ocean. A unique ecosystem forms in
delta regions, like the Santee delta in South Carolina or the Mississippi delta in Louisiana.
Students should also understand how important this water is to human activities.

Human beings are dependent upon water for survival, not only for drinking but for agriculture and industry as well.

Dams have been place along some rivers in order to produce hydroelectric power and to offer recreation in the lakes that form
behind the dams.

Lakes, rivers, and the ocean contain sources of food and minerals.
Earth is 71% water with about 3% usable fresh water. Students need to know where this water is, how it moves, and why it is so
important as an abiotic factor within an ecosystem.
It is not essential for students to know the development of river systems or the features that form along river systems. Karst
topography and the formation of deposits in caves is also not necessary. Glaciers, their movement and deposits, are not part of this
indicator.
7-4.6 Renewable and Nonrenewable Resources
It is essential for students to know that natural resources are materials from Earth that are used by living things. Some resources can
be replaced and reused by nature; these are renewable resources. Natural resources that cannot be replaced by nature are
nonrenewable.
Renewable: Air, water, soil, and living things are renewable resources. The water cycle allows Earth’s water to be used over and
over. New soil is formed to replace soil that has been carried away by wind and water (although new soil forms very slowly). Trees
and other new plants grow to replace those that have been cut down or died. Animals are born to replace animals that have died.
Renewable resources are replaced through natural processes at a rate that is equal to or greater than the rate at which they are being
used.
Nonrenewable: Fossil fuels (coal, oil, natural gas), diamonds and some other minerals are nonrenewable. They exist in a fixed
amount and can only be replaced by processes that take millions of years. Nonrenewable resources are exhaustible because they are
being extracted and used at a much faster rate than the rate at which they were formed.
Students need to realize that natural resource can be depleted, used to the point that they are no longer available. Conservation
measures are necessary.
Depletion of nonrenewable resources is understandable because they are known to be in a non-replenishing supply. If renewable
resources are used at an increasing rate so that they cannot be naturally replaced fast enough, they too can be depleted. Depletion of a
natural resource, such as trees, can contribute to global warming.
Conservation :The wise use of a natural resource. As the number of people on Earth gets larger, the need for natural resources
increases. The terms reduce, reuse, recycle and protect are important ways that people can be involved in conservation of natural
resources.
It is not essential for students to know human consumption of resources affect the physical and chemical cycles and processes of
Earth.
7-5.1 Matter
It is essential for students to know that matter is composed of extremely small particles called atoms and that atoms are the smallest
part of pure substances that cannot be broken down into simpler substances.
It is not essential for students to know the subatomic particles, for example, protons, neutrons, and electrons, which compose atoms.
7-5.2 Classify matter as element, compound, or mixture on the basis of its composition.
It is essential for students to know that matter can be classified on the basis of its composition as follows:
Elements
Elements are pure substances that cannot be changed into simpler substances. Elements are composed of one
type of atom.
Compounds
Compounds are pure substances that are composed of two or more types of elements. Compounds can only be
changed into simpler substances called elements by chemical changes (7-5.10), which are not as easy as
separating mixtures into their components.
Mixtures
Mixtures are composed of different substances that are mixed together
It is not essential for students to know that atoms combine to form molecules, which are the smallest part of compounds. Students
also do not need to know that mixtures can be heterogeneous or homogeneous.
7-5.3 Properties of Metals and Nonmetals
It is essential for students to know that metals and nonmetals are two major groups of elements that have different physical
properties as follows:
Metals
Physical properties of metals include the following:
Luster
Having a shiny surface or reflecting light brightly
Conductors
Heat and electricity move through them easily.
Malleable
Ability to be hammered into different shapes
Ductile
Ability to be drawn into a wire
High density
Heavy for their size
Nonmetals Physical properties of nonmetals include the following:
Dull
Not shiny
Nonconductors
Heat and electricity do not move through them easily
Brittle
Break or shatter easily
It is not essential for students to know the chemical properties of metals versus nonmetals, or the electron arrangement in atoms of
metals versus nonmetals.
7-5.4 Periodic Table
It is essential for students to know how to use the periodic table to identify the basic organization of elements. The elements on the
periodic table are identified with numbers increasing from left to right across each row of the table. Along with this number (atomic
number) there is also a symbol that identifies each element on the table. There are two large sections of elements on the periodic
table. On the periodic table there is a zigzag line on the right side of the table. Metals are to the left of this line. Nonmetals are to the
right.
Families
Also called groups, are columns of elements on the periodic table that have many similar properties; they are
usually numbered 1-18. A family of elements has some chemical characteristics that are similar.
Metals
Groups of elements generally located on the left side of the periodic table. Examples on metals are: Sodium
(Na), Calcium (Ca), Iron (Fe), and Aluminum (Al).
Nonmetal Families are generally located on the right side of the periodic table. Examples of
nonmetals are: Chlorine (Cl), Oxygen (O), Sulfur (S), and Iodine (I).
It is not essential for students to know how each element gets its atomic number (no subatomic particles are part of this standard).
They do not need to know the names of the individual families or groups of elements or to identify metalloids.
7-5.5
Translate chemical symbols and the chemical formulas of common substances to show the component parts of the
substances (including NaCl [salt], H20 [water], C6H1206 [simple sugar], 02 [oxygen gas], C02 [carbon dioxide], and N2
[nitrogen gas]).
It is essential for students to know that chemical symbols show the atoms of the elements composing a substance. Atoms of
common elements have different symbols as follows:
Symbol
Element
Na
Cl
H
0
C
N
Sodium
Chlorine
Hydrogen
Oxygen
Carbon
Nitrogen
Chemical formulas are constructed from the symbols of the elements composing the substances. Elements are made up of one type of
atom and their formulas have one symbol. Compounds are composed of more than one element and their formulas have more than
one type of symbol showing the different atoms that compose the compound. In a chemical formula, the numbers as subscripts show
the ratio of the number of atoms of the different elements in the compound.
It is not essential for students to know other chemical symbols and chemical formulas.
7-5.6
Distinguish between acids and bases and use indicators (including litmus paper, pH paper, and phenolphthalein) to
determine their relative pH.
Acids
Acids can be identified by their sour taste (lemons and oranges contain acids)—but students should not use a taste
test on laboratory chemicals; by their reaction with some metals (for example, zinc), and by their reaction with
bases to form a neutral pH solution.
Bases
Bases can be identified by their bitter taste (soapsuds have a bitter taste)—but students should not use a taste test
on laboratory chemicals; by their slippery feels when rubbed between thumb and fingers---but some strong bases
burn the skin so this test should not be used; and by their reaction with acids to form a neutral pH solution.
pH
pH is a measure of the concentration of solutions of acids and bases and is measured on a scale of 1-14. A basic
solution has a pH greater than 7 and an acidic solution has a pH less than 7. If a solution is neither an acid nor a
base, it has a pH of 7 and is called neutral. Pure water has a pH of 7. The stronger the acid, the lower the pH (less
than 7) while the stronger the base, the higher the pH (greater than 7).
Indicators
Indicators are substances that can be used to determine the whether a solution is an acid or base. The following
indicators can be used to determine relative pH
Litmus paper
pH paper
Phenolphthalein
Blue litmus paper turns red in an acid, and stays blue in a base. Red litmus paper turns
blue in a base, and stays red in an acid. Both red and blue litmus paper turn purple in a
solution that is neutral (neither an acid nor a base).
pH paper can turn a series of colors in solutions of pH. The color of the paper is
compared to the chart of the vial to determine the pH.
Phenolphthalein turns magenta in a strong base and stays clear in an acid
It is not essential for students to know the specific colors of pH paper at given pH ranges or how to neutralize a solution to form
water and salt.
7-5.7
Identify the reactants and products in chemical equations.
It is essential for students to know that when substances are mixed and at least one new substance is formed, a chemical reaction has
occurred.
Chemical equations
Reactants
Products
Are used to represent chemical reactions that have occurred. They contain the chemical formulas (75.5) for the substances that are mixed and the new substance(s) that are formed. An arrow separates
them.
The substances that are mixed in a chemical reaction are called the reactants and appear on the left
side of the arrow in a chemical equation.
The new substances that are formed in a chemical reaction are called the products and appear on the
right side of the arrow in a chemical equation.
For example, the following chemical equation shows the formation of water (H20) from oxygen (02) and hydrogen (H2). The reactants
are oxygen (02) and hydrogen (H2), located on the left side of the arrow. The product, water (H20), is on the right side of the arrow.
2H2 + 02 →
2H20
Reactants →
Products
It is not essential for students to know how to balance chemical equations by adding coefficients in front of the chemical formulas
or to name the various types of chemical reactions that occur (for example, single displacement, double displacement, decomposition,
or synthesis).
7-5.8
Explain how a balanced chemical equation supports the law of conservation of matter.
It is essential for students to know that the amount of matter does not change during a chemical reaction; only the atoms are
rearranged to form new substances. The law of conservation of matter is based on countless experiments in which the mass of the
reactants has been found to equal the mass of the products. The law of conservation of matter states that matter can neither be created
nor destroyed, but can be changed in form. In other words, the total mass of the material(s) before the reaction is the same as the total
mass of material(s) after the reaction.
A balanced chemical equation has the same number of each kind of atom on both sides of the arrow. When students multiply the
number in front of the chemical formula in the equation by each number written below the symbol of the atoms in the formula, the
number of each kind of atom on the left side of the arrow must equal the number of each kind of atom on the right side of the arrow
for the equation to be balanced
In the chemical equation for the reaction of water (liquid) changing to hydrogen and oxygen (gas)
2H20  2H2 + 02

There are 2 x 2 Hydrogen (H) = 4 Hydrogen (H) atoms on the left of the arrow and 2 x 2 Hydrogen (H) = 4 Hydrogen (H) atoms
on the right of the arrow;


There are 2 x 1 Oxygen (O)= 2 Oxygen (O) atoms on the left of the arrow and 1 x 2 Oxygen (O) atoms on the right of the arrow;
(if no number appears in front of the formula or below the atom, it is an understood “1”).
Therefore, there are the same numbers of atoms of hydrogen (4) and oxygen (2) on both sides of the equation and the equation is
said to be balanced.
Since there are the same number of each kind of atom on both sides of the arrow and atoms represent kinds of matter, the amount of
matter is the same on both sides of the equation, which supports the law of conservation of matter.
It is not essential for students to know how to add numbers in front of chemical formulas to balance chemical equations. They must
only recognize a balanced equation. They do not have to know how to create the chemical formulas for substances. They must only
analyze given formulas for common substances to show the component parts.
7-5.9
Compare physical properties of matter (including melting or boiling point, density, and color) to the chemical
property of reactivity with a certain substance (including the ability to burn or to rust).
It is essential for students to know that physical properties of matter can be observed and measured without changing the kind of
matter being studied. Chemical properties are not usually visible. They can be recognized only when substances react chemically
with one another, that is, when they undergo a change in composition. The following physical properties can be used to help identify
a substance:
Melting Point
Boiling Point
Density
Color
Melting point is the temperature at which a solid can change to a liquid. The temperature at which a pure
substance melts is unchanging. Therefore, the melting point of a pure substance can be used as a physical
property for identifying it. Ice melts to form water at 0 0C or 32oF.
Boiling point is the temperature at which a liquid changes state into a gas. The liquid starts to form bubbles
throughout, which grow larger, rise to the surface, and burst. This temperature is unchanging for a given
substance, at sea level, and can be used to identify that substance. The boiling point for pure water is 100oC or
212oF.
Density, defined qualitatively, is the measure of the relative “heaviness” of objects with a constant volume, is
the mass of a given volume of a substance. The density of a given substance is unchanging and can be used as a
physical property to identify it. The density of water is a universal standard: 1 milliliter of water (at 4 oC) equals
1 cubic centimeter of water equals 1 gram of water. The density of water is 1 g/mL or 1 g/cm 3 or 1g/cc. Lead
for example is a very heavy, dense metal. The density of lead is much greater than the density of the very light
metal, aluminum.
Color of a given substance is distinctive and can be used to help identify a substance.
Chemical properties can also be used to help identify a substance. Chemical properties are not usually visible. Chemical properties
can be recognized only when substances react chemically with one another, that is, when they undergo a change in composition.
 Chemical reactivity is the tendency of a substance to undergo a chemical reaction usually with other specific substances.
 When a substance reacts with oxygen quickly and releases heat and light energy, the process is called burning.
 When a substance, for example iron, reacts with oxygen and water slowly, the process is called rusting.
It is not essential for students to calculate the density of substances if given the mass and the volume of the substances.
7-5.10
Compare physical changes (including changes in size, shape, and state) to chemical changes that are the result of
chemical reactions (including changes in color or temperature and formation of a precipitate or gas).
It is essential for students to know that physical changes do not change the identity of a substance. When a substance changes state,
the substance does not change identity. A change in state, therefore, is a physical change. When substances change in size or shape,
they do not change identity; therefore, these changes are also physical changes.
When the following changes occur, however, the substance usually changes identity; therefore, the changes are chemical changes:
Color change
When a substance changes color, the chemical composition of the substance has usually changed;
therefore, this is a chemical change.
Temperature change
When substances change temperature after being mixed with other substances, the chemical
composition of the substances has usually changed; therefore, this is a chemical change.
Precipitate formation
When two or more liquids are mixed and a solid (precipitate) forms, the chemical composition of the
substances has usually changed; therefore, this is a chemical change.
Gas formation
When substances are mixed or heated and a gas is given off, the chemical composition of the
substances has usually changed; therefore, this is a chemical change.
It is not essential for students to identify the type of chemical change that has occurred, nor to identify a reaction as exothermic or
endothermic depending on the temperature change.