Transcript BIODIVERSITY - Lamont High

Biological Diversity
Section 2
Reproduction and Survival
2.1 A Closer Look at Variation
Variation is one of the most critical
aspects of species survival.
Variation may not always be easy to
identify. It may be a behavioural
tendency or a genetic modification.
Variations enable some individuals
within a species to survive while
others of the same species will
perish.
Inherited and Non-inherited
Characteristics
Inherited (heritable) characteristics
are traits which are passed on to
offspring directly from their parents.
These traits are passed on inside the
genetic material.
Heritable traits include structural and
distinguishing characteristics such as
eye color, hair type, skin color and
earlobes.
Non-inherited characteristics are
acquired and not necessarily passed
on from generation to generation.
Ex. Athleticism, artistic ability,
leadership qualities are all learned
during the early years of life.
Discrete and Continuous Variations
Discrete variations are differences
in characteristics that have a
definite form.
Individuals within a species have
one of two possible expressions of
the characteristic.
Discrete Variation:
Hitchhiker's Thumb
Straight thumb
Widow’s peak
roll tongue
Continuous variations are
differences in characteristics that
have a multitude of variations, such
as height, shoe size, or hair color.
Variation and the Environment
Some variations may be influenced by
interactions with the environment. These
variations are not inherited.
Examples include:
Change in the pigmentation of skin color
due to sun exposure.
Height and weight can be influenced by
diet.
Now do Check and Reflect
p. 29 #1-3, and 6
2.2 Asexual and Sexual Reproduction
A. Asexual Reproduction
Asexual reproduction involves only
one parent.
All of the offspring are identical to
the parent.
There are different types of
asexual reproduction:
1. Binary Fission
only single-celled organisms
reproduce in this way. The cell
splits into two cells and each one is
identical.
Ex. bacteria, amoeba, algae
2. Budding
the parent organism produces a bud (a
smaller version of itself) which eventually
detaches itself from the parent and
becomes a self-sufficient individual identical to the parent. Corals reproduces
this way, but do not detach themselves
Ex. hydra, yeast, coral, sponge
3. Spore Production
spores are similar to seeds, but are
produced by the division of cells on the
parent, not by the union of two cells. One
parent may produce many spores, each of
which will grow into a new individual,
identical to its parent.
Ex. fungi, green algae, moulds, ferns
Q: How do spores survive unsuitable growing conditions?
(p.30)
4. Vegetative Reproduction
The reproduction of a plant not involving a
seed, including: cuttings, runners, suckers,
tubers.
Ex. coleus plant, spider plants,
strawberries, aspen, potatoes
Q: Explain why a cluster of aspen trees turn
color at exactly the same time (p.31)
Read the infoBIT on p.30 about
Parthenogenesis
Q: define parthenogenesis In Greek it means:
List 5 organisms who may
reproduce by parthenogenesis:
B. Sexual Reproduction
Sexual reproduction usually involves two
individual organisms (some plants and
animals can self-fertilize).
The offspring inherit half of their
genetic information from one parent and
the other half from the other parent.
Sexual reproduction involves specialized
gametes (reproductive cells that have
only one role - to join with another
gamete during reproduction).
1. Sexual Reproduction in Animals
Male gametes are called sperm cells
and the female gametes are called
egg cells or ova.
During mating, the sperm cell and
the egg cell unite to form a
fertilized combination of cells called
a zygote.
The zygote divides first into two
cells and those cells continues to
divide over and over(cleavage)
resulting in the development of an
embryo.
The embryo develops into a multicellular organism inside the female (in
most mammals) or, outside (in an egg
shell) in other animals.
Draw the events from fertilization to
development of an embryo (p. 32).
Weird Fact: In seahorses the female
inserts her oviduct into the male’s
brood pouch where the eggs are
fertilized and develop.
In a matter of speaking the male sea
horse is pregnant!
2. Sexual Reproduction in Plants
Sexual reproduction in plants also
involves gametes.
Male gametes and female gametes
join during fertilization to produce
a zygote and then an embryo.
Most plants produce both male and
female gametes, while some produce
only one or the other.
Pollen contains the male gametes
and is found on the stamen.
Ovules contain the female gametes
and are found in the pistil.
Pollination occurs when pollen is transferred
from the anther of the stamen to the
stigma of the pistil.
Cross-pollination occurs when pollen from
one plant is carried to the stigma of
another plant by wind, water, animals or
insects (bees or butterflies).
Cross-fertilization occurs when a grain of
the pollen forms a long tube which grows
down the style into the ovary.
The gametes unite to produce a zygote,
which then develops into an embryo.
•This usually happens inside a seed
which protects the embryo. The seed
also provides food (cotyledon) for the
embryo as it begins growing when
conditions are suitable.
•Plants produced as a result of crossfertilization are not identical to either
parent plant, but will have a
combination of characteristics from
both parents.
Video Link: Plant Reproduction
plant reproduction
MonD: Nye: Flowers
3. Organisms that Reproduce both
Sexually and Asexually
Sponges are organisms that can produce
both sexually and asexually. Most
plants that produce seeds can also
reproduce asexually (cuttings, runners).
Advantages and disadvantages of Asexual and
Sexual Reproduction
Asexual Reproduction
Sexual Reproduction
ADVANTAGES
does not require any
specialized cells
only need one parent
produce many offspring very
quickly
advantage where the
environment doesn't change
very much (ex. bacteria).
ADVANTAGES
• Greater genetic variation
within a species
• Variation usually helps a
species survive when the
environment changes.
DISADVANTAGES
little genetic variation
less adaptability to a new or
changing environment
DISADVANTAGES
• Takes a lot of energy
• Takes a lot of time
• Comparatively smaller
populations are produced.
Define hermaphrodite (p.32)
Give 2 examples.
Do Check and Reflect p.36 #1-6, and 11
Do Section Review p.37 # 1,3,5,9,10
Do Flower Lab p.34