Transcript Chapter 2 Parents & Offspring

Chapter 2
Parents & Offspring
Lesson 1: Reproduction
Lesson 4: Traits and Heredity
I CAN…
 Explain sexual and asexual
reproduction.
 Compare and contrast sexual
and asexual reproduction.
Focus Question:
Where do living things
come from?
Key Vocabulary
 Sexual reproduction – the production of a
new organism from two parents.
 Fertilization – the joining of an egg cell
and a sperm cell to form a new offspring.
 Asexual reproduction – the production of
a new organism from a single parent.
Key Vocabulary
 Vegetative Propagation – asexual
reproduction in plants that produce new
plants from leaves, roots, or stems.
 Runners – plant stems that lie on or
under the ground and sprout up as new
plants.
Where do living things
come from?
 Living things come from OTHER LIVING
THINGS.
 The survival of a species depends on its
ability to produce new members.
 Every organism comes from a parent
organism through the process of
reproduction.
Reproduction
 Reproduction involves the transfer of
genetic material from parent to offspring.
 The genetic material contains information
that controls how the new individual will
look and function.
 There are two main types of
reproduction: sexual & asexual
Sexual Reproduction
 A sperm cell from a male and an egg cell
from a female join in a process called
fertilization.
 The fertilized egg cell contains genetic
material from both parents.
 The fertilized egg goes on to develop into
a new individual who will have some
characteristics, or traits from each parent.
Traits
 A trait is a characteristics of a living thing.
 What are some traits that we can name?
Asexual Reproduction
 Produces a new offspring that has the
same genetic information as the parent.
 No female or male sex cells combine
during this process.
 Since there is only one parent, genetic
information is not mixed and the offspring
is identical to the original parent.
Asexual Reproduction
 There are organisms that reproduce asexually
in all six kingdoms.
 All members of the bacteria kingdom and most
protists replace asexually.
 Most fungi and many plants can reproduce like
this.
 Animals such as jellyfish, corals, worms, and
some echinoderms as well as some kings of
lizards, frogs, fish, and insects can form
offspring asexually.
Methods of
Asexual Reproduction
 Splitting – the organism makes a copy
of its own genetic material and then splits
into two cells.
 Budding – a small part of the parent’s
body grows into a tiny and complete
version of the parent and then breaks off
and continues to grow.
Other Methods of
Asexual Reproduction
 Sometimes female eggs just develop into a new
animal without fertilization.
 Example: Queen honeybee
 Vegetative Propagation – produces new plants
from leaves, roots, or stems.
 Runners are plant stems that lie on or under the
ground and sprout up as new plants.
 Example: strawberry plants, grasses, aspen trees, ferns
How do sexual and asexual
reproduction compare?
 Asexual reproduction is convenient
because the parent does not have to rely
on another organism.
 Sexual reproduction promotes variety in
a species that can better adapt to a
changing environment.
I CAN…
 Describe how traits are
passed from one generation
to the next.
 Explain dominant and
recessive traits.
Focus Question
How are traits passed
from one generation
to the next?
Key Vocabulary
 Heredity – the passing down of traits from
parents to offspring.
 Inherited trait – a trait that an offspring receives
from its parents.
 Instinct – a way of acting or behaving that an
animal is born with and does not have to learn.
Key Vocabulary
 Gene – contains chemical instructions for
inherited traits.
 Dominant trait – one that dominates, or
masks, another form of that trait.
 Recessive trait – one that is hidden, or
masked, by another form of the trait.
Key Vocabulary
 Pedigree – a chart used to trace the
history of traits in a family.
 Carrier - any individual who has inherited
the gene for a trait, but does not show
that trait physically.
Heredity
 What causes us to look the way we look?
 Heredity applies to all organisms.
 In plants, flower color and plant height are
inherited traits.
 Inherited trait is a trait that an offspring
receives from its parents.
 Some inherited traits in humans include
dimples, hair and eye color, facial features,
and even the way you laugh.
Can heredity affect
behavior?
 Some behaviors, such as instincts, are
inherited.
 An instinct is a way of acting or behaving that
an animal is born with and does not need to
learn.
 A learned behavior is developed during the
course of a lifetime.
 Learning results from practice and experience.
 The ability to learn helps animals to survive.
How are traits inherited?
 What controls the traits you inherit?
 Why do some people look more like one
parent than another?
 Gregor Mendel answered a lot of these
questions.
 He was an Austrian monk who studied
and discovered the basic principles of
heredity.
Inheridited Traits
 After years of experimenting, Mendel determined
that inherited traits are passed from parents to
offspring through reproduction.
 He believed that each inherited trait is controlled by
two factors – the offspring receive one of these
factors from each parent.
 These are called genes.
 A gene is a chemical instruction for inherited traits.
 They are stored on cell structures called
chromosomes, which are found in the nucleus of
the cell.
Who picks the traits we
get?
 Mendel concluded that for every trait
there is a dominant form and a recessive
trait.
 Each form of the trait can be represented
by a letter.
 Capital letters = Dominant traits
 Lowercase letters = Recessive traits.
Dominant vs. Recessive
 Mendel’s findings are important because
they apply to all organisms.
 In humans, genes that determine the
shapes of your earlobes, hairlines, and
thumbs all have dominant and recessive
forms.
 Dominant traits tend to be expressed
more frequently than recessive traits.
How do we trace
inherited traits?
 Some of the traits controlled genes are
easy to see, like hair color.
 Genes also control many things you
cannot see.
 Some individuals carry a trait without
showing evidence of that trait.
 You can find out who carries what trait by
using a pedigree.
Pedigree
 A pedigree is a chart used to trace the history of
traits in a family and are used to study heredity
patterns.
 Parents and offspring are shown in a pedigree.
 Horizontal lines connect parents and vertical lines
connect parents to offspring. Males are
represented as boxes and females are shown as
circles.
 Individuals with a dominate trait are shaded and
unshaded shapes represent recessive individuals.