Chapter 4:
Animal Growth
and Heredity
Lesson 1: How Does Cell Division Affect Growth?
Lesson 2: How are Characteristics Inherited?
Lesson 3: What Other Factors Affect Characteristics?
Lesson One:
VOCABULARY:
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Life Cycle: The stages that a living thing passes
through as it grows and changes.
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Mitosis: The process by which most cells divide.
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Chromosome: A threadlike structure in the nucleus,
made up of DNA.
Lesson One: How Does Cell Division
Affect Growth?
Growth and Development
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All living things begin life as a single cell.
In plants and animals, the cells start dividing.
The fully formed plant or animals is made up of
trillions of cells.
Even in adult organisms, cells continue to divide and
replace the worn out cells.
The new cells have the same function as the old cells.
Lesson One: How Does Cell Division
Affect Growth?
Growth and Development
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As living things grow, they must pass
through several stages which make
up the life cycle.
Some animals change a great deal as
they grow into adults.
Butterflies and other insects have one
kind of body while young and
another type of body when they
become an adult.
The stages they go through as they
grow are called metamorphosis.
Other animals do not change as
much during their life cycle and look
pretty much the same when they are
young as when they are old except
bigger.
Lesson One: How Does Cell Division
Affect Growth?
CELL DIVISION
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The process by which most cells
divide is called mitosis.
Mitosis is controlled by the cells
nucleus.
The nucleus contains threadlike
structures called
chromosomes.
Chromosomes are made up of
chemical DNA.
DNA has the information
needed to direct a cells function
and tell the cell when to divide.
Lesson One: How Does Cell Division
Affect Growth?
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In mitosis, each new cell gets a
copy of the parent’s
chromosomes.
This passes along the DNA
which is why the cells look and
function just like the parent
cells.
New cells replace damaged
tissue which is called regeneration.
In humans, regeneration
happens mostly for healing
wounds.
However, some animals can
regenerate an entire body part
(like a starfish).
Lesson One: How Does Cell Division
Affect Growth?
Sexual and Asexual
Reproduction:
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Sexual reproduction happens when
two cells from two different
individuals join and form a zygote.
Organisms that reproduce sexually
have 2 types of cells: Body cells
and reproductive cells (or gametes).
Gametes contain only half the
number of chromosomes (23
chromosomes) as body cells.
Once two gametes join, they have
the same number of chromosomes
as a body cell (46 chromosomes)
has.
Lesson One: How Does Cell Division
Affect Growth?
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Some organisms have only one cell.
When the cell divides, the whole organism
reproduces.
In asexual reproduction there is no joining of
cells from different parents.
Lesson Two: How Are
Characteristics Inherited?
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VOCABULARY
Inherited trait: A characteristic passed from parents to
their offspring.
Recessive trait: A trait that appears only if an
organism has two factors, or genes, for that trait.
Dominant trait: A trait that appears even if an
organism has only one factor, or gene, for that trait.
Gene: Part of the chromosome. It contains the DNA
code for an inherited trait.
Lesson Two: How Are
Characteristics Inherited?
How Characteristics are Inherited
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Inherited traits are characteristics
passed from parents to their
offspring.
The way traits are passed from
parents to offspring interested
Gregor Mendel who studied this.
Mendel found that a trait is
controlled by a pair of factors (one
from each parent).
Mendel also learned that factors
can skip a generation.
Inheritance in all organisms
(including people) works this way.
Lesson Two: How Are
Characteristics Inherited?
Dominant and
Recessive Traits
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Mendel did hundreds of crosses of pea
plants and found that first generation
plants were always tall.
Mendel believed the first generation
plants had a hidden factor for shortness.
In pea plants, tallness is a strong or
dominant trait.
Even if an organism has only one factor
for a dominant trait, that trait will appear.
Shortness in a plant is a weak or
recessive trait.
A recessive trait appears only if an
organism has two factors for that trait.
If both a dominant factor and recessive
factor are present, the dominant trait
always appears.
Lesson Two: How Are
Characteristics Inherited?
Adaptations
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Arctic foxes live in very cold
places. An arctic fox has
adaptations that keep it warm
in the winter.
Adaptations helps a living
organism meet their basic
needs in order to survive,
find a mate, find shelter, hunt
or hide.
Adaptations are passed from
parent to offspring and are
inherited traits.
Lesson Two: How Are
Characteristics Inherited?
Adaptations
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of adaptations:
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The first kind is physical.
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Example: An arctic fox has white
fur in winter which helps it hide
and more easily sneak up on prey.
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The second kind of
adaptation is behavioral.
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Example: Snakes only move
around before sunset or after
sundown. During the hottest part
of the day they will hide under a
rock to stay cool.
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The third kind of adaptation
is a life process.
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Example: A human’s body
produces sweat. This helps keep
the body from getting too hot.
Lesson Two: How Are
Characteristics Inherited?
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Survival and Reproduction:
All animals have adaptations for survival.
For example: porcupines have an adaptation that
protects them from predators.
Adaptations help animals survive so that they can
reproduce.
If a species cannot successfully reproduce, it may
become extinct.
Extinction is the death of all organisms
of a species.
Lesson Two: How Are
Characteristics Inherited?
Genes:
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Today, Mendel’s “factors” are called “genes”.
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A gene is part of a chromosome.
Genes contain the DNA code (information) for
inherited traits.
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Lesson Three: Other Factors
that Affect Characteristics
VOCABULARY:
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Instinct: is a behavior (way of acting) that an organism
inherits.
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Learned behavior: a behavior that an animal acquires
through experience.
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Environment: all of the things in an organism’s
surroundings that affect it.
Lesson Three: Other Factors
that Affect Characteristics
Instincts:
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A bird making a nest and a cat
grooming itself are examples of
instincts.
An instinct is a natural behavior.
Most instincts help an animal
survive in its surroundings.
Since instincts are inherited, they
are passed from parents to
offspring.
Instincts are not just behaviors of
one animal.
Instincts are shared by all members
of a species.
Lesson Three: Other Factors
that Affect Characteristics
Learned Behaviors:
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Most cats are born with an instinct
to hunt.
But they need to learn hunting
skills from adult cats.
Knowing how to hunt is a learned
behavior.
A learned behavior is a behavior
that an animal obtains by doing
something.
Not all learned behaviors are for
survival. (tricks)
Some animals can learn behaviors
that are helpful to people.
Lesson Three: Other Factors
that Affect Characteristics
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Environmental Influences:
Some behaviors are neither instinctual or learned.
They are a result of environmental influences.
An organism’s environment is everything in its surroundings that
affect it.
This may include water, food, air, landforms, and other living
things.
When an environment changes, all things that live there are
affected.
Often times animals must move in order to survive.
Human activities can sometimes change an environment.
Sometimes the environment causes a
physical change in living things
(pollution or poison can damage the DNA of living things.)