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Asexual reproduction. OVERVIEW. Clone : an identical genetic copy of its parents Bread mold comes from a single mold spore A duplicate tree growing from the bottom of another tree Asexual Reproduction : only 1 parent is required to produce offspring . - PowerPoint PPT Presentation
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ASEXUAL REPRODUCT
ION
OVERVIEWClone: an identical genetic copy of its
parents Bread mold comes from a single mold sporeA duplicate tree growing from the bottom of
another tree
Asexual Reproduction: only 1 parent is required to produce offspring
Clones can also be created artificially (agricultural or horticultural industries, or biomedical labs) Trying to create heartier breeds and increase
plant production Clone healthy genes to replace mutated ones Potentially cloning the genes of extinct
animals like Tasmanian Tigers!
We might be able to use cloning to reproduce extinct species like Tasmanian
tigers!
Types of Asexual Reproduction
There are 5 main methods of asexual reproduction:
1. Binary Fission2. Budding 3. Fragmentation 4. Vegetative Reproduction5. Spore Formation
1. Binary Fission A single parent cell replicates its genetic
material, dividing into 2 equal parts Method used by small, one-celled eukaryotic
organisms like amoeba
Ex.: Amoebas Have between 30-40 chromosomes Chromosomes duplicated during
mitosis
Binary fission is the only method of reproduction for some bacteria!
No nucleus = no mitosis!
Instead, one ring of DNA is replicated...
Under ideal conditions, it can replicate every 20 min. Ex. Streptococcus bacteria
Mutations can occur during binary fission! Mutations in the DNA
of bacteria can make it very resistance to antibiotics
2. Budding Areas of an individual undergo mitosis
and cell division, developing into an identical organism
Used by some multicellular organisms (hydras and sponges) that only have a few different cell types
The “buds” might detach from the parent and become a new individual OR remain attached
1. Hydra develops a “bud”
2. The bud develops a mouth and tentacles
3. When it’s fully formed the daughter hydra detaches from parent
4. The daughter is fully independent
Budding is great for organisms like sponges because they attach to rocks and move very little. Colonies can grow in the same area or break off and colonize new locations.
3. Fragmentation Occurs when a piece of an organism
breaks apart (ex. injury) and each fragment develops into a clone of the parent
Ex.: Starfish If a broken arm contains enough DNA it
can develop into an identical copy
Plants can also reproduce by fragmentation IF the environment doesn’t change and IF there are enough nutrients available.
Example: Eurasian milfoil Introduced to North America Chopped up by propellers and spread
through lakes
4. Vegetative Reproduction Occurs when special cells (usually in plant
stems and roots) divide repeatedly to form structures that will eventually develop into an identical plantDevelop off of the bulb
or as sprouts (“eyes”)
Ex.: Tulips, daffodils, hyacinth bulbs, and potatoes
Disadvantage Daughter plants grow very close to
parent plants Will complete for soil, nutrients, and light
Benefits of Vegetative Reproduction
Potatoes #1 tuber crop in world Used globally
Common Camas An important part of the First Nations
diet Also used for trading
Human Assisted Methods of Vegetative Reproduction
1. CUTTINGS The plant grower removes a part of the
stem (or leaf/root) and plants the cutting in a special growing medium
Plant hormones, which are chemical messengers, are often applied to the cut stem
Hormones signal nuclei to stimulate cell division, causing some cells to develop into root tissue
House plants can reproduce in this method
2. GRAFTING Stems called “scions” are attached to
the rotted stock (“rootstock”) of a similar plant
Often used for apple trees and rose plants
Another form called “budding” is used to grow apple trees
Advantages: Can help scion benefit from a more
rigorous root system
Produce fruit within 2-3 years instead of 5-10 years
Helps control eventual size of plant
5. SPORE FORMATION Method used by some bacteria, micro-
organisms, fungi (ex. bread mold), mosses, and ferns
Reproduction through the formation of single-celled spores
Spores: a reproductive cell that grows into a new individual by mitosisVery light in weight Rely on wind or water for
transportation
If conditions are right (enough moisture and food, and proper temperature) a new individual will grow wherever it lands
Many spores have tough outer coatings that allow them to survive in harsh conditions (drought or extreme temp.) until the conditions are right
Summary of Asexual Reproduction