Asexual Reproduction Flashcards
What is the definition of Asexual Reproduction?
is the reproduction of an offspring from only one parent
What does ‘natural cloning’ mean of an offspring?
Its means that the offsprings are identical or ‘clones’ of the parent
How do prokaryotes uses asexual reproduction?
use it to produce new offspring by binary fission
How do eukaryotes uses asexual reproduction?
they reproduces asexually via mitosis
Number of parents of parental contribution in Asexual Reproduction
One
Number of parents of parental contribution in Sexual Reproduction
Two
Process involved in Asexual Reproduction
Binary fission (prokaryotes), cell replication with mitosis (eukaryotes)
Process involved in Sexual Reproduction
Gamete Production involving meiosis (eukaryotes)
Is Fertilisation absent or present in Asexual Reproduction?
Absent
Is Fertilisation absent or present in Sexual Reproduction?
Present
Offsprings in Asexual Reproduction
No genetic variability, offsprings are clones of a single parent
Offsprings in Sexual Reproduction
Offsprings differ from one another and their parents
Rate of offspring production in Asexual Reproduction
Faster
Rate of offspring production in Sexual Reproduction
Slower
Advantages of Asexual Reproduction
- Rapid population growth
- Only one single organism is required- no need to find a mate
- Every member of the population can give rise to offsprings (either male or female)
Disadvantages of Asexual Reproduction
- No genetic variation
- If conditions change and become unfavourable, organisms may die out or if a diseases spreads through the population
- If organisms are genetically identical, this reduces the chance or ability of an organism adapting to a new environment or conditions.
Examples of species that can use BOTH Asexual and Sexual Reproduction
Many insects (aphids), algae, most plants and fungi species
Using BOTH Asexual and Sexual Reproduction
Some species can change depending on season for example when conditions are favourable, reproduce asexually to build population numbers but if conditions change, reproduce sexually to increase genetic variability to ensure survival
Examples of Asexual Reproduction:
- Binary Fission (prokaryotes)
- Splitting in single celled eukaryotes
- Spore formation in fungi
- Natural cloning in animals
- Budding and Virgin birth
- Vegetative Reproduction
Binary Fission (prokaryotes)
Is the splitting of a prokaryote into 2
Why do prokaryotes through binary fission grow rapidly and exponentially?
Due to the simplicity and providing conditions are favourable they can grow rapidly and exponentially.
How do unicellular eukaryotes such as Amoeba and Paramecium divide by asexual reproduction?
This process is also referred to as binary fission but different to the prokaryotic process, as it involves the process of mitosis.
Budding
Involves the detachment of a small group of cells that move and set up elsewhere.
Examples of organisms that use budding to increase their population:
Sponges and Hydra
Parthenogenesis (also termed ‘Virgin birth’)
Reproduction occurs without fertilisation. The egg is produced without the sperm and via mitosis.
Examples of organisms that use parthenogenesis:
Many insects or aphids and invertebrates. Often rarely seen in vertebrate animals such as Whiptail Lizard. TYPICALLY IN AN ALL FEMALE POPULATION>
Are offsprings identical or different in Parthenogenesis?
Offsprings produced are identical to the parent.
Obligate Parthenogenesis
Are species that only reproduce via Parthenogenesis. These animals are termed unisexual and usually have a complete absence of males in the population.
Examples of species in Obligate Parthenogenesis:
Whiptail Lizard, some snakes, rocktail lizards and australian gecko.
Facultative Parthenogenesis
Used in species when needed. I.e. When there are no males available for reproduction. When males re-appear, they go back to using sexual reproduction
Examples of species in Facultative Parthenogenesis:
Komodo dragon
Spore Formation (Fungi)
Spores are produced via mitosis and are dispersed to develop into new organisms that are genetically identical to the parent- Eg. Bread Mould
Sporangia
Spores formed by mitosis and suspended in an aerial structure called Sporangia When released from the sporangia, the spores are carried through the air and form in a new location
Asexual Reproduction in Plants
Referred to as ‘vegetative reproduction’
Runners
Are special stem that grow over the ground and grow away from the parent. At alternate nodes, new buds give rise to roots, leaves, flowers and fruits.
Eg. strawberry plant
Cuttings
Clones of the parent by taking a cut of shoots and roots or leaves and replanting them
Eg. Roses
Rhizomes
Buds and roots sprout from modes along a rhizome to produce a new daughter plant
Suckers
New shoots that arise a distance from the parent plant
Plantlets
Grow on the parent and once they reach a certain size, they drop off and produce a new plant.
How are plants cloned?
Via Cutting but more recently, plant tissue cultures are being used
Tissue Cloning
Produces identical copies of a plant from a small tissue sample
Examples of plants that use Tissue Cloning:
Orchids, carnations and Australian native plants
Advantages to Tissue Cloning
- Slow growing plants can be produced in large numbers
- Plants can be cultured all year around
- Virus free tissue can be produced
- Cultured plants can be transported between countries
Tissue Culture
Step 1:
Start with a small piece of a healthy plant (leaf, bud, stem). It must contain meristematic tissue.
Tissue Culture
Step 2:
Pieces are sterilised and placed in a test tube with a culture medium (agar and nutrients) and treated with cytokinin .
What is cytokinin?
plant hormone that stimulates shoot formation
Tissue Culture
Step 3:
Test tubes are incubated
Tissue Culture
Step 4:
After a few weeks, new shoots will appear. They are than cut into several pieces and recultured in other test tubes again (subculturing).
Tissue Culture
Step 5:
After number of rounds of subculturing, shoots have auxin added to stimulate root production.
Tissue Culture
Step 6:
Once cultures have formed roots, stems and shoots, they are than planted in sterile compost and sand.
How are animals produced?
They’re naturally produced via sexual reproduction which requires an egg to be fertilised by a sperm.
What are the processes that Artificial cloning can involve?
- Cloning by embryo splitting
- Cloning using somatic cell nuclear transfer
Embryo Splitting
Is the artificial splitting on an embryo in its early stages. This produces twins and sometimes triplets.
When are embryos usually split?
During IVF (invitro fertilisation)
Are offsprings in embryo splitting identical to the parent or each other?
Identical to each other
Somatic Cell Nuclear Transfer
Step 1:
Remove the nucleus from a cell (enucleating)
Somatic Cell Nuclear Transfer
Step 2:
Transfer nucleus from one cell to an enucleated cell (a cell without a nucleus)
Somatic Cell Nuclear Transfer
Step 3:
Fuse somatic cell with the enucleated cell
Somatic Cell Nuclear Transfer
Step 4:
These animals have become clones of the animal in which the nucleus from step 2 was taken
To achieve Somatic Cell nuclear transfer, which cells can be used?
Fetal or embryonic cells. However, this can now be done using adult cells.
Dolly the Sheep
Was the first cloned animal from an adult cell using somatic cell nuclear transfer
What did Dolly the Sheep open doors too?
That animals could potentially be cloned from any animal including those that have past their reproductive period or those that have recently deceased.
Examples of cloned animals:
- Megan and Morag (cloned sheeps)
- Dolly the sheep
- Matilda (lamb)
- Mayzi and Suzi (calves)
- Cc (cat)
- Snuppy (dog)
Disadvantages to Cloning:
- Low success rate (can take up to 200 implants before the surrogate becomes pregnant)
- Once surrogate is pregnant, clones have a low survival rate
- High rate of abnormalities in surviving clones
- Rapid ageing in cloned animals
Public Opinion (Cloning) - Agree
- Provides benefit
- Source of tissues
- Possible medical advantages- growing
replacement ‘parts’ for humans and animals
Public Opinion (Cloning)- Disagree
- Against nature
- Where does it stop?
- Australia has an act that was passed in 2002 (The prohibition of human cloning act)