Transcript Sunken Lesson Animal Growth and Heredity

Sunken Lesson
Animal Growth and
Heredity
Grade 5
How Organisms Grow
• Nearly all body cells produce exact
copies of themselves.
• Producing identical cells allows
organisms to function properly and
grow.
Cell Division
• The nucleus controls everything a
cell does and tells it when to divide.
• Cell division is called mitosis.
• During mitosis a cell makes exact
copies of itself.
Mitosis
• To prepare itself for mitosis, a cell
makes an exact copy of its
chromosomes
• During mitosis, the chromosomes
pull apart, and the cell membrane
pinches in at the middle
• Two new cells are formed that are
identical to the parent cell
Regeneration
• Regeneration is a kind of healing, or
tissue replacement
• When our skin is damaged, we heal
through regeneration of new skin
cells
• Some plants and animals can
regenerate major body parts – lizards
can grow new tails and starfish can
grow new arms
Asexual Reproduction
• Many primitive organisms such as
one celled bacteria reproduce by
simple cell division
• Only one parent is required for
asexual reproduction
• Yeast reproduce by budding – a new
bud forms on the parent cell, grows,
and then separates to form a new cell
Sexual Reproduction
• Most organisms require two parents
to reproduce
• Parent cells go through meiosis to
copy its chromosomes and divide
• Then they go through a second stage
of division where they split their
chromosomes in half.
• Gametes are formed with half the
chromosomes of the parent cells
• Two gametes join to form a one new
cell
Life Cycles
• Most organisms grow and mature
through several distinct stages of life
• These stages of life are called life
cycles
• All life cycles start with a young
organism
Direct Development
• In direct development, the young
organisms are identical to the adult
organism except for size
• The young grow larger, but keep the
same body features, such as shape,
all their lives
Metamorphosis
• Some organisms change greatly
from the time that they are young to
the time that they are adults.
• The changes in the shape or
characteristics of an organisms body
as it grows and matures are called
metamorphosis
Complete metamorphosis
• Complete metamorphosis has four
stages: egg, larva, pupa, adult
Incomplete
metamorphosis
• Incomplete metamorphosis has three
stages: egg, nymph, adult
Inherited Traits
• Many characteristics of an organism
are passed from parent to offspring
• Hair or fur color, eye color, attached
or free earlobes, short or long
eyelashes, tongue rolling, and
dominant thumbs are examples of
traits that are inherited
• Traits can be dominant, or strong
and seen, while others are recessive,
or weak and hidden
Genes
• Genes are structures on
chromosomes that are found in a
cell’s nucleus
• Genes contain the code for the traits
that an organism gets from its
parents
Recessive Traits
• If a recessive trait (such as light
brown fur in a rabbit or blue eyes in a
human) is seen, then the organism
MUST have TWO genes for that trait.
• That means that they received the
recessive gene from both parents
Dominant Traits
• If a dominant trait (such as dark fur
or brown eyes) is seen, then the
organism only needs one gene for
that trait.
• That means they only had to receive
the dominant gene from one parent