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This is the outline for chapter 2. Make sure your child is studying a little bit every day so that they can be
ready for the upcoming test.
5th Grade Chapter 2 Outline
How Do Organisms Grow and Reproduce:
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Cell division:
o Cells are basic units of life
o As a cell grows, it divides and forms new cells
o Some organisms are made up of one cell. When the single cell that makes up a onecelled organism divides, the newly formed cells separate.
o When the cells of many celled organisms (ex. dogs, cats, people) divide, they do not
separate. They stay together and keep on dividing. As the cells divide, the organism
grows and changes.
o Your body always needs to make new cells so that they can replace old cells that wear
away or die.
o When a cell starts to divide, it makes copies of all its parts. After the cell divides, the
new cell will have parts that are identical to the ones the original cell had.
o The cells nucleus controls all activities of the cell
o Chromosomes: threadlike structures in the nucleus of a cell that control the cell’s
activities
Producing new individuals:
o Reproduction is different in many-celled organisms than it is in one-celled organisms.
o Reproduction in many celled organisms:
 When many celled organisms reproduce, 2 parents contribute to form the
offspring.
 Two kinds of cells, called reproductive cells are formed. On is called an egg cell.
The other a sperm cell.
 These cells have only half the as many chromosomes as the other cells in an
organism’s body.
 Fertilization occurs when a sperm cell and an egg cell unite.
 Fertilized egg: The cell that results when an egg cell and a sperm cell
unite
 A fertilized egg gets the chromosomes from the sperm and the
chromosomes that were in the egg cell. This results in the same number
of chromosomes that the other cells of the parent have.
 This fertilized egg grows and develops into a new organism by dividing
over and over and over and over again!!
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Many celled organisms do not look EXACTLY like either of their parents. They
get some characteristics from mom, and some from dad. These differences are
called variations.
Reproduction in Flowering plants:
o Pollination is the first step in the reproduction of a flowering plant. It takes place when
pollen grains are moved from a stamen to the sticky part of a pistil.
o In most flowering plants, pollen from the stamen of one plant travels to the pistil of
another plant of the same kind.
o One way pollen travels is by sticking to an insect’s body and as it travels from flower to
flower, the pollen grains stick to the second flower’s pistils.
o Another way pollen travels is through wind.
How Are Traits Passed Along?
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Traits that pass from parents to their offspring are inherited .
Recall that chromosomes in the nucleus of your cells carry information that control the activity
of your cells. This information also determines what traits you have
Chromosomes contain traits that determine all of an organisms characteristics.
A gene is the part of a chromosome that carries information that controls a trait
Dominant and Recessive Genes
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Different forms of the gene for a trait may carry different information about it. Often one form
of the gene hides the effect of the other form
Recessive gene: a gene whose expression is hidden by dominant gene
Dominant Gene: A gene that can hide the effect of a recessive gene
Hybrid: An individual that has a dominant and a recessive gene for a triat
PUNNET SQUARES: These are diagrams that help us see the probabilities of genes that could be
inherited. We will do these in class so I will not go into further explanation here.
Mutations:
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Mutation: A permanent change in the structure of a gene or chromosome.
Some mutations do not harm the organism. For example a cat whose eyes resulted in a
mutation and ended up with one green eye and one blue eye.
Some mutations can harm an organism: For example, Hemophilia , a disease in which the blood
does not clot properly, is caused by a mutation. This could be passed on to offspring.
Some squirrels get mutations in the color of their fur and end up with white fur. This is a
disadvantage because when it cannot blend in with a tree like most squirrels do, this results in
difficulties hiding from a predator.
Mendel and Inheritance of Traits
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Gregor Mendel, an Austrian monk, studied inheritance in green garden pea plants during the
mid-1800s.
He made careful observations and kept exact records of the results. He counted and recorded
exactly how many plants with each trait he found at each step of every experiment.
He used mathematics to describe and analyze the results of his experiments
Studying Genes and Chromosomes:
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Thomas Hunt Morgan experimented with fruit flies to learn about chromosomes.
Fruit flies have traits that make them easy to use during experiments, such as variety of eye
colors and wing colors, their chromosomes are also bigger than in most other cells
In 1952, scientists identified a large molecule called DNA as the material that makes up
chromosomes and carries information about inheritance.
Rosalind Franklin produced pictures of DNA molecules that gave clues to their structure.. that
they were twisted, like a spring.
James Watson and Francis Crick used the information from the pictures made by Franklin to
design a model of DNA’s structure.
Genes were identified as sections of DNA molecules.
Using Understanding of Inheritance:
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Selective Breeding: Breeding plants or animals with certain traits to produce offspring with
those traits. This is mainly used for plants and farm animals so that farmers can sell the best
vegetables and meat
Lesson Review 1:
1. How do cells divide?
2. How do cells produce new individuals?
3. How does a flowering plant reproduce?
4. Compare the number of chromosomes in an organisms body cells with the number in its reproductive
cells.
Lesson 2 review:
1. How do offspring get traits like those of their parents?
2. How do dominant and recessive genes differ?
3. How does a mutation affect a trait?
4. What fraction of the offspring will probably have rough fur if both parents are a hybrid?
Lesson 3 Review:
1. How did Gregor Mendel learn about inheritance of traits?
2. Explain how genes and chromosomes are related?
3. How does knowing about inheritance help farmers and food producers?
4. How are ears of corn today different from those grown thousands of years ago?