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; contains DNA (cell’s heredity information) / Present / Present
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 nucleus (bacteria) / *** Eukaryotes have a nucleus (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 essentialthat 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 shapedRod shaped bacteria are known as bacilli

SpiralSpiral 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 withCilia (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 withFlagella (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
Bacillus bacteria
Causes anthrax
Rod shaped / Streptococcus pneumonia
Cocci bacteria
Causes pneumonia
Round shaped / Treponema pallidum
Spirilla bacteria
Causes syphilis
Spiral shaped
Euglena (single celled protest) / Paramecium (single celled protest) / Amoeba (single celled protest)
Plant like protist that moves with a flagellum; looks green; makes own food w/ chloroplasts; live in fresh water; contractile vacuole pumps out excess water / Animal like protist that moves w/ cilia (tiny hair-like structures) which help propel it and sweep food toward its food passageway / 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
  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

Cellular processes for survival

PhotosynthesisThe 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.

RespirationBreaks “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.

EliminationRids 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.

MitosisCell 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 provides animals with oxygen
radiant energy + 6 (CO2) + 6(H20) 
C6H12O6 + 6(O2) / Plant and animal cells use ATP for energy. Mitochondria convert glucose to ATP. ATP is made through a process known as cellular respiration.
C6H12O6 + 6(O2)  6(CO2) + 6(H2O) + ATP

CELL CYCLE:

(1) Interphase: cell carries out normal activities, growing in size; cells components are copied nearthe 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 fordominant 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 forrecessive 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 InheritanceBiological 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 toknow 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 essentialfor 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:

CellsThe 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.

TissuesA 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.

OrgansAre 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.

SystemsA 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:

System

/ Major Organs / Function (s)
Circulatory / Heart / Causes blood to flow through the body by it pumping action
Blood vessels (arteries, capillaries and veins) / Tubes that carry blood throughout the entire body
Respiratory / Nose / Collects air from the environment and moistens and heats the air before it enters the trachea
Trachea / The windpipe; moves air from the nose to the lungs
Bronchi / Tubes that move air from the trachea to the lungs; one bronchus leads to each lung; part of each bronchusis outside the lung and part is inside.
Diaphragm / The dome-shaped muscle that aides in the breathing process
Digestive / Mouth / Begins to break down food into smaller pieces through mechanical digestion; saliva in the mouth starts the process of chemical digestion
Esophagus / The transport tube that carries chewed food to the stomach
Stomach / Continues the process of mechanical digestion; secretes enzymes that perform some chemical digestion of food
Small intestines / The organ where most of the chemical digestion of food takes place; nutrients from food are also absorbed through the small intestines
Large 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
Rectum and anus / The rectum is a short tube that stores solid waste until it is eliminated from the body through the anus.

System

/ Major Organs / Function (s)
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 / An ancillary organ to the digestive system that functions to produce enzymes that help break down starches, proteins, and fats in the small intestine.
Gallbladder / An ancillary organ to the digestive system that functions to store bile produced by the liver.
Excretory (Urinary) / Kidneys / The two kidneys function to get rid of urea , excess water, and some other waste materials which are eliminated in urine
Ureters / Tubes which connect each kidney to the bladder
Bladder / A saclike muscular organ which stores urine until it is released from the body
Urethra / Tube through which urine passes before it is removed from the body.
Nervous / Brain / 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.
Spinal cord / 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.
Peripheral nerves / 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.
Muscular / Skeletal muscles / Voluntary muscles that are attached to bones and provide the force needed to move your bones
Smooth muscles / Involuntary muscles that control many types of movement in the body (i.e, digestion)
Cardiac muscles / Involuntary muscle that forms the heart
Skeletal / Bones / Provide shape and support for the body and protection for many organs and structures; some bones produce blood cells; some store minerals

System

/ Major Organs / Function (s)
Integumentary / 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.

It is not essential for students to know the major organs of the reproductive system, immune system, endocrine system.