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ASEXUAL & SEXUAL REPRODUCTION
ASSESS YOUR LEARNING
Due Monday, November 3, 2014
#s 1-8
REPRODUCTION PRODUCES NEW INDIVIDUALS OF A SPECIES.
The way a species reproduces determines how much variation the new individuals will have.
REPRODUCTION…
Can produce new individuals that are identical to or very different from one another.
Which produces greater variation in individual organisms… Asexual or Sexual Reproduction?
ASEXUAL REPRODUCTION
Involves only one parent.
All offspring that result from asexual reproduction are identical to that parent.
In other words, the adult makes an exact copy of itself.
There are several different forms of asexual reproduction.
1. BINARY FISSION
BINARY FISSION
Only 1 cell organisms, and some protists, such as amoebas and some algae, reproduce by binary fission.
During binary fission, a cell splits exactly in two, producing two identical individuals.
Binary = two
Fission = splitting or dividing (cleavage)
REMEMBER…
The Protista Kingdom consists of unicellular lifeforms (lifeforms with only one cell) who have a nucleus.
The primary difference between protists and monera (bacteria) is that protists are more complex, having a nucleus.
2. BUDDING
ORGANISMS…
Such as hydra and yeast reproduce asexually by budding.
During budding, the parent produces a small “bud”, or a smaller version of itself.
In most animals (like the hydra) and unicellular fungus (yeast), the bud detaches and becomes a new individual identical to its parent.
In some (such as coral) the offspring remains attached to the parent, forming a large structure composed of many identical individuals.
SPORE PRODUCTION
SPORES Similar to seeds, but are produced by the
division of cells of the parent, not by the union of two cells.
ONE INDIVIDUAL Will produce many spores, and each spore
can develop into a new individual identical to the parent.
Most fungi, green algae, some molds, and non-flowering plants, such as ferns, reproduce by producing spores.
4. VEGETATIVE REPRODUCTION
THERE ARE DIFFERENT FORMS OF VEGETATIVE REPRODUCTION
Vegetative reproduction is the reproduction of a plant that does not involve the formation of a seed.
Most plants can reproduce this way.
IF YOU TAKE A “CUTTING” FROM A PLANT…
And place it in water, the cutting will grow roots and eventually develop into a whole new plant.
Many plants, such as strawberries or spider plants, grow runners that produce new plants.
TUBERS… Such as potatoes on a potato plant, and
bulbs, from which tulips develop, are also forms of vegetative reproduction.
THE ROOTS OF AN ASPEN TREE…
Form a shoot called a “sucker”; if the sucker becomes separated from the original tree, it will grow into a new aspen tree.
IN ALL OF THESE FORMS OF VEGETATIVE REPRODUCTION…
The individual new plants that are produced will be genetically identical to their parent plant and to one another.
DIAGRAM IT!!!
Make a labeled diagram illustrating the kinds of asexual to show how an organism reproduces by that form.
Compare your diagrams.
Describe any similarities and differences between them.
Hand in your work
PARTHENOGENESIS:
“Virgin Birth” in Greek.
Describes the process that transforms unfertilized eggs into mature organisms.
In bees, unfertilized eggs become the male drones, and fertilized eggs become female workers and queens.
Has been observed in snakes and plants (figs)
SEXUAL REPRODUCTION
SEXUAL REPRODUCTION…
Usually involves 2 individuals.
Most animals and flowering plants reproduce sexually.
OFFSPRING…
Will have a mix of characteristics of both individuals.
DOES SEXUAL REPRODUCTION ALWAYS INVOLVE A MALE AND A FEMALE?
SEXUAL REPRODUCTION IN PLANTS & ANIMALS…
Relies on the union of specialized cells known as gametes.
MALE GAMETES:
Sperm cells.
FEMALE GAMETES:
Egg cells (ova)
THE UNION OF THE SPERM AND EGG
Happens during mating and is called fertilization.
THE CELL CREATED BY THE JOINING OF…
2 gametes (egg & sperm) is known as a zygote.
THE ZYGOTE
Is the first cell of a new individual. The zygote then divides into two cells. The same divisions are repeated during a process called cleavage.
CONTINUED CELL DIVISION:
Results in a new multicellular life form known as an embryo.
DEPENDING ON THE SPECIES
Development of the embryo may occur inside the female parent, or outside, inside the egg.
SEXUAL REPRODUCTION IN PLANTS
Most plants produce both male (sperm) and female (egg) gametes.
Some produce only female and only male.
Pollen: contains the male gametes; found in the stamen (male part of plant).
Ovules: contain the female gametes; found in the pistil (female part of the plant).
POLLINATION OCCURS WHEN POLLEN IS TRANSFERRED FROM THE ANTHER TO THE STIGMA.
CROSS-POLLINATION…
Occurs when the pollen of one plant is carried to the stigma of another by wind, water, or animals.
CROSS-FERTILIZATION
Occurs when a grain of this pollen produces a long tube that eventually grows down the style into the ovary that contains the ovules.
In most plants, the embryo is produced inside a seed.
THE SEED…
Protects the embryo and stores food the the embryo for when it starts to grow into a new individual.
Unlike animals, the new embryo may not begin to grow for some time (remain dormant) until it has suitable growing conditions.
ASEXUAL REPRODUCTION
Produces lots of individuals very quickly-less energy
E.G. Bacteria- every 20 minutes; 12 hrs, 10 million copies of itself
Great advantage in environments that don’t change much-warm/moist
If conditions change/become unfavourable, the entire population may be wiped out.
E.G. Every single one of the 10 million could be wiped out by an anti-biotic.
Advantages Disadvantages
SEXUAL REPRODUCTION
Provides lots of variation which helps a species survive environmental change.
Takes a lot of energy and time.
Can only produce a limited number of offspring.
Advantages Disadvantages
ORGANISM THAT REPRODUCE SEXUALLY & ASEXUALLY
Most plants can. Seeds (sexually) or Cuttings/Bulbs/Runners
(asexually)
When plants reproduce by asexually, the offspring is genetically identical to the parent.
SOME ANIMALS CAN REPRODUCE SEXUALLY & ASEXUALLY:
Aphids (small insects); throughout the growing season, females produce live female young without fertilization (asexual reproduction).
SOME ANIMALS CAN REPRODUCE SEXUALLY & ASEXUALLY:
In the fall, when the temperature drops, the female produces males & females who then reproduce sexually, and lay eggs that will hatch in the spring.
SOME ANIMALS CAN REPRODUCE SEXUALLY & ASEXUALLY:
Sponges can also reproduce sexually and asexually.
SOME ANIMALS CAN REPRODUCE SEXUALLY & ASEXUALLY:
Jellyfish alternate between sexual and asexual reproduction.
HERMAPHRODITES
Can produce both male and female gametes (common garden worms & slugs).
Prefer to mate with other individuals, but in times of environmental stress, can fertilize themselves.
In humans, hermaphroditism is an extremely rare sex anomaly. A true hermaphrodite is an individual who has both ovarian and testicular tissue (both reproductive organs).
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