Transcript File

What is Variation?
• Variation is the
diversity among a set
of objects
– Genetic variation is
then differences in
inherited traits
(genetics) that exist
among the members
of a species
Observing Variation
• Tall vs Short people
• Curly vs straight hair
• Bent vs straight
•
•
•
thumb
Attached vs separate
earlobes
Pointed vs smooth
hairline
Rolling your tongue
Heritable vs Non-Heritable
Characteristics
• Heritable Characteristics: are passed on
from generation to generation
• (ex) Eye Colour
• Non-Heritable Characteristics: are acquired
from the environment
• (ex) a tan
Discrete vs Continuous Variation
• Discrete Variation:
•
differences in characters
that have a definite form
(ex) being albino
– You are either albino
or not
• Continuous Variation:
•
differences in
characteristics that have
a range of forms
(ex) human height
which is a range
Environment
• Variation can result
•
from interactions
between individuals
and the environment
(ex) If you had 2
identical plants and you
put one in the sun and
one in a dark closet.
– One will be green and
bushy
– The other will be yellow
and wilted
Try This….
• Close your eyes and clasp your hands
• Which thumb is on top??
• Is this discrete or continuous variation?
What is Asexual Reproduction?
• Asexual
Reproduction:
involves only one
parent and doesn’t
require the fusion
of sex cells
– The offspring is
identical to its
parent
4 Types of Asexual Reproduction
1. Binary Fission:
when cell splits
in 2, producing
2 identical
individuals
http://bioweb.wku.edu/courses/BIOL115/Wyatt/Micro/Monera.htm
2. Budding: When a unicellular parent cell
produces an offspring by forming a
protrusion of itself.
http://www.rgs.edu.sg/bio2000/video/yeastbud.mov
3. Spore Production: Producing reproductive
cells through cell divisions of parent cells
Reproduction Without Seeds
• Vegetative Reproduction:
reproduction of seed plants that does
not involve the production of seeds
• Reproduce from:
•Stems and roots
•Runners: long stems that grow
along the soil of the surface and
produce new plants (ex) raspberries
•Rhizomes: stems that grow
underground stems and produce new
plants
Suckers
New plants
that form on
roots
Cuttings
• A piece of a
plant that is used
to make a new
plant
• usually a stem
and few leaves
Grafting
• A technology to
reproduce plants
that involve
attaching part of
one plant to a
second plant
What is Sexual Reproduction?
• Sexual Reproduction:
reproduction involving
the exchange of
genetic material
between two
individuals resulting in
offspring that are
genetically different
from the parents.
Sexual Reproduction
• Sexual reproduction
•
relies on the union of
sex cells called
gametes
Offspring of the
parents will have
mixed characteristics
Sexual Reproduction in Animals
• Male gametes are called sperm
• Female gametes are called egg cells or
ova
• When a sperm and egg cell come together
this is called fertilization
– Only 1 sperm cell can fertilize an egg cell
• The cell created thru
fertilization is called a
zygote
– A zygote is formed right
when the 1 sperm cell
enters the egg
– The egg then gives off a
chemical that keeps the
other sperm from
fertilizing it
• The zygote is the first
cell of a new individual
• The zygote then divides into
2 cells
– Divisions are repeated through
a process called cleavage
• The zygote then turns into a
multi-cellular embryo
– Depending on the species the
development of the embryo
can occur inside the female
parent or outside the parents
in an egg
What is pollination?
• Pollination: The transfer of pollen
from the male pollen sacs to the female
stigma
Function of flower
• To attract pollinators with colorful petals,
scent, nectar and pollen
The Parts of a Flower
Reproductive floral organs:
female
• Stigma – is where pollen
•
•
•
sticks to
Style – is the long tube
that connects stigma to
ovary and contains the
pollen tube
Ovary – enlarged
structure at the base of
style that protects the
ovule.
Ovules – contains female
part of the seed plant that
becomes the seed
Sexual reproduction
• In animals is easy because you have
separate male and female individuals.
• In flowering plants it’s not so easy, because
most flowers have both male and female
parts in them, called perfect flowers.
Strategies to avoid selfpollination
• Perfect flowers have both male and female
organs, so plants have strategies to avoid
self-pollination:
• 1. Timing – male and female structures
mature at different times
• 2. Structure –male and female organs
prevent
self-pollination (imperfect flower)
• 3. Biochemical – chemical on surface of
pollen and stigma that stops the pollen tube
from being formed in the same flower
Pollination and Fertilization
• For pollen to successfully
•
•
fertilize the egg, there
must be crosspollination
Pollen sticks to the
stigma, starts growing a
pollen tube
Cross-Fertilization
begins when
tube begins to grow
toward the egg
How do plants get pollen from
one plant to another?
• Because plants are rooted in the ground,
they must use different strategies:
• WIND POLLINATION
• ANIMALS
ANIMAL POLLINATORS
• Many flowering plants rely on animals for
cross-pollination:
• Insects – bees, wasps, flies, butterflies,
moths
• Birds – hummingbirds, honey creepers
• Mammals – bats, mice, monkeys
• Even some reptiles and amphibians!
A word about pollen…
• The shape and form of pollen is related to its
method of pollination…
• Insect-pollinated species
have sticky of barbed
pollen grains
• Wind-pollinated species
is lightweight, small and
smooth (corn pollen)
Advantages and Disadvantages of
Asexual Reproduction
• Are able to reproduce rapidly
– (ex) strep
– (ex) white blood cells
• Limited variation
• If conditions become unfavourable whole
populations can be wiped out
• Puts all energy into reproduction of itself
Advantages and Disadvantages of
Sexual Reproduction
• Reproduce a lot slower
– (ex) human’s
• Provides lots of variation
• Takes a lot of energy into making enough
gametes so that fertilization can occur
– Have a limited amount of offspring
– (ex) sperm and pollen
Organisms that reproduce
Asexually AND Sexually
• Some species can reproduce
both sexually and asexually
– (ex) aphids
• During the growing season,
females reproduce asexually
producing more females (asexual)
• Over the summer these female
young mature
• in the fall asexually produce male
and female offspring
• Males and females mate and lay
eggs for a new colony that
hatches in the spring