Transcript Chapter 15: Biological Diversity and Heredity

Chapter 15: Biological Diversity
and Heredity
Foundations
Ms. Johnson
Objectives
• Living things have developed special characteristics called
adaptations, which enable an organism to live in a particular
environment or habitat.
• Reproduction is the process by which an organism produces new
individuals of its own kind.
• Asexual reproduction involves only one parent and produces
offspring identical to the parent.
• Sexual reproduction involves two parents, male and female, and
produces offspring not identical to either parent.
• All cells come from other cells through the process of cell division.
• Genetic information is passed from one generation to the next
through chromosomes during reproduction.
• When two genes match for a trait, an individual is called pure for
that trait. When two genes differ for a trait, the individual is called
hybrid for that trait.
• In a hybrid, often only one trait is visible; this is called dominant
trait. The trait that is not exhibited in a hybrid is called a recessive
trait.
• A change in a gene is called a mutation.
Vocabulary
• Adaptations
• Habitat
• Reproduction
▫ Sexual
▫ Asexual
• Fertilization
• Cell division
• Gene
Diversity of Life
• Different environments have
promoted different changes in
living things.
• Living things have
adaptations that enable
them to survive under a given
set of conditions.
▫ Adapted for life in water,
land, soil, air, etc.
Diversity of Life
• Adaptations permit an organism to live in its
own particular environment (habitat).
• Example:
▫ Cactus plant has an extensive root system that
helps it reach what little water there is in the
desert.
Diversity of Life
There are millions of different types of plants and animals. Scientists classify
organisms in various ways to better understand their similarities and
differences.
Organism
Habitat
Adaptation
Function
Arctic Hare
Arctic
White fur in
winter
Provides
camouflage from
predators
Monkey
Rain forest
Grasping tail
Acts as an extra
hand to help
movement
through trees
Cactus
Desert
Waxy skin
Reduces water
loss from
evaporation
Reproduction
• All living things come from other living things.
• Reproduction: the process by which an
organism produces offspring (new individuals of
its own kind)
• Each particular organism is called a species.
• There are two types of sexual reproduction:
asexual and sexual.
Reproduction
• Asexual reproduction:
involves only one parent
▫ The offspring created are
identical to the parent.
• Sexual reproduction:
involves two parents and
▫ Produces offspring that are
not identical to either parent.
▫ Female parent produces an
egg cell and the male
produces the sperm cell.
• The joining together of egg and
sperm is called fertilization.
Life Cycles
• Some young animals look like smaller version of
their parents.
▫ Ex. Puppies, baby elephants, tigers
• Some animals, however, change dramatically
during their life that the young look nothing like
the adults.
▫ Ex. Frogs, Insects
• Life cycle: the changes that an organism
undergoes as it develops and produces offspring.
Life Cycles
• Eventually the young will look
like the adult.
• Information is carried from
the parent to the offspring
determining how they will
look.
• This information gets passed
on from generation to
generation.
Cellular Reproduction
• All cells come from other cells through the
process of cell division.
▫ One “parent” cell divides into two new “daughter”
cells
• The parent cell passes genetic information on to
the daughter cells in the form of
chromosomes.
▫ Chromosomes are thread-like structures that
contain DNA
• Chromosomes also give the cell (or organism) its
individual characteristics called traits.
Cellular Reproduction
• One-celled organisms
reproduce through a kind of
cell division called mitosis.
• In this process a cell divides
into two identical daughter
cells each with the same
number of chromosomes as
the parent.
• Multi-cell organisms duplicate
themselves to build new
tissues and repair damage
tissues by mitosis.
• Any organism that reproduces
asexually does so through
mitosis.
Sexual Reproduction
• Some organisms reproduce
sexually with two parents.
▫ Involves the two special
reproductive cells, one from
each parent.
▫ The sex cells (sperm and egg)
have only half the number of
chromosomes that other cells
have.
▫ Formed through meiosis
• The sex cells join together in
what is called fertilization.
Inheritance of Traits
• A piece of genetic information
that influences a trait is called
a gene.
• These two genes can be the
same or different.
▫ Example: the type of earlobe
you have is determined from
the genetic information you
received from your parents.
 Ears can either be attached
or free
• If both genes match for a trait,
the same trait will appear and
it is said to be pure.
• If you have differing genes for
a trait (attached and free) you
are said to be hybrid.
Mendelian Genetics
• Gregor Mendel (1822-1884)
investigated pea plants and
determined that some genes
could be dominant over others.
▫ The gene that is not exhibited
is recessive
• Mendel crossed pure tall pea
plants and pure short pea plants
▫ He observed all the plants were
tall and concluded that tall was
dominant.
• He then crossed two hybrids
and observed most were tall
with a few short which he
concluded some of the plants
still had the gene for tall.
Mendelian Genetics
Organism
Trait
Dominant
Recessive
Human
Eye color
Brown
Blue
Human
Earlobe
Free
Attached
Human
Blood type
A or B
O
Fruit Fly
Wing
Normal
Vestigial
Fruit fly
Eye color
Red
White
Pea plant
Height
Tall
Short
Pea plant
Pea color
Yellow
Green
Pea plant
Seed shape
Round
Wrinkled
Using a Punnett Square
• We can predict the possibility of an offspring if
we know the types of the genes in the parents.
• The represent a gene, we use a capital letter for
the dominant trait.
▫ R for red
• We use a lowercase of the same letter for a
recessive trait. Type of Genes Representation Appearance
▫ r for white
Pure red
RR
Red
Hybrid red
Rr
Red
Pure white
rr
White
Using a Punnett Square
• A punnett square can be
used to predict the probability
of an organism inheriting a
given trait.
• The genes for each parent are
placed on the top and the side.
R= gene for red eyes
r= gene for white eyes
Types of Genes
Appearance
Probability
RR- pure dominant
Red eyes
¼ (25%)
Rr- hybrid dominant
Red eyes
2/4 (50%)
Rr- pure dominant
White eyes
¼ (25%)
Mutations
• Genetics accidents do occur- they are called
mutations.
▫ Sometimes genetic material does not reproduce
properly.
▫ Can be caused by a natural accident or by something in
the environment.
• If the mutation is harmful to the organism, it is less
likely to survive and reproduce.
• If the change is beneficial to the organism, it will be
better able to survive and reproduce.
▫ The new genetic information can be passed on to the
new generation.
Mutations
• Natural selection: favors those organisms that
that are best able to survive and reproduce.
• After many generations and mutations that
organism may look and behave differently from its
ancestors that it has become a new species.
▫ This process is called evolution.
• Evolution accounts for the great diversity among
living things.
Questions?
Homework:
Page 181
Page 185-88