Asexual Reproduction 2 1

7/29/2019 Asexual Reproduction 2 1

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Asexual

Reproduction



What is asexual

reproduction?• Asexual reproduction is a mode of

reproduction by which offspring arise from

a single parent, and inherit the genes of

that parent only, it is reproduction which

does not involve meiosis, ploidy reduction,

or fertilization.

http://en.wikipedia.org/wiki/Meiosis

http://en.wikipedia.org/wiki/Ploidy

http://en.wikipedia.org/wiki/Fertilization

http://en.wikipedia.org/wiki/Fertilization

http://en.wikipedia.org/wiki/Ploidy

http://en.wikipedia.org/wiki/Meiosis



ASEXUAL REPRODUCTION

• involves one parent only.

• Parent cell splits into two toproduce new cells(MITOSIS).

• Offspring therefore identicalto the parent (CLONE).

• Results in a lack of variation

and diversity between parentand offspring and amongoffspring.

• Gametes and fertilization areNOT required.

SEXUAL REPRODUCTION

• Involves two parents (male

and female).

• Two sex cells (gametes)made by MEIOSIS fuse toform the offspring.

•

Offspring therefore hascharacteristics from bothparents but are not identicalto the parents or oneanother.

• Results in variation and

diversity between parent andoffspring and amongoffspring.

• Gametes and fertilizationARE required.



What is asexual

reproduction?• A more stringent definition is

agamogenesis which refers to

reproduction without the fusion of

gametes. Asexual reproduction is the

primary form of reproduction for single-

celled organisms such as the archaea,

bacteria, and protists

http://en.wikipedia.org/wiki/Gamete

http://en.wikipedia.org/wiki/Single-celled_organism


http://en.wikipedia.org/wiki/Archaea

http://en.wikipedia.org/wiki/Bacteria

http://en.wikipedia.org/wiki/Protist

http://en.wikipedia.org/wiki/Protist

http://en.wikipedia.org/wiki/Bacteria

http://en.wikipedia.org/wiki/Archaea




http://en.wikipedia.org/wiki/Gamete



• The different modes through

which asexual reproduction takes

place are binary fission, sporeformation, vegetative reproduction

and budding.



Advantages of asexual

reproduction• 1. Large numbers of offspring are reproduced very

quickly from only one parent when conditions arefavourable.

• 2. Large colonies can form that can out-complete other organisms for nutrients and water.

• 3. Large number of organisms mean that species maysurvive when conditions or the number of predatorschange.

• 4. Energy is not required to find a mate



Disadvantages of asexual

reproduction• 1. Offspring are genetic clones. A negative mutation can

make asexually produced organisms susceptible todisease and can destroy large numbers of offspring.

• 2. Some methods of asexual reproduction produceoffspring that are close together and compete for foodand space.

• 3. Unfavourable conditions such as extreme

temperatures can wipe out entire colonies.



Vegetative Reproduction

• Vegetative reproduction is a form of

asexual reproduction in plants, where

parts of the plant fall off and develop into

new plants. Potato tubers are oneexample of a plant that used this form of

reproduction. Since asexual reproduction

doesn't require another partner, or pollentransfer it is very quick and is guaranteed.



Vegetative Reproduction

• This is very good for people using potatoes in

their products, because reproduction is very fast,

so they can make more potatoes, and hence

make more money. The main disadvantage of this form of reproduction, is that the new plants

will all grow very close to each other and to the

parent. This will cause a struggle for soil,

nutrients and light, and will consequently causethe plants to be less healthy.



POTATO



ASEXUAL: NATURAL VEGETATIVE PROPAGATION

•

Occurs when new plants are formed from theoutgrowths of old ones.

• Examples are:

• Runners where the stems run horizontally from aplant and new plants form at nodes (strawberry,pumpkin).

• Bulbs are underground buds and new buds grow

from the parent one (onion).

• Plantlets are tiny plants that grow along the marginsof certain leaves. Eventually the plantlets fall off anddevelop into new plants (the Leaf of Life).



RUNNERS



BULBS



PLANTLETS



ASEXUAL REPRODUCTION:

ARTIFICIALVEGETATIVE PROPAGATION

• Gardeners and farmers often use artificial

means when they want to propagate more

of a plant that is of good quality becausethe offspring will be identical to parent.

•

These methods include:1. Cuttings

2. Grafting



ASEXUAL REPRODUCTION: ARTIFICIAL

VEGETATIVE PROPAGATION

• Gardeners and farmers often use artificial

means when they want to propagate more

of a plant that is of good quality becausethe offspring will be identical to parent.

•

These methods include:1. Cuttings

2. Grafting



PROPAGATION BY CUTTINGS

Parts of a plantare cut off andgiven suitableconditions sodeveloping

their own rootsand shoot andbecome a newplant.

Examples aresugarcane,yam andhibiscus.



PROPAGATION BY GRAFTING

• A shoot (the scion)from a young plantbearing fruits or flowers is attachedto the stem of analready

established rootsystem (the stock).The new plant thatgrows hasbeneficialcharacteristics of both the stock andscion e.g. mango,citrus and rose-bushes.







SPORE FORMATION



Vegetative Propagation

It is a process where a plant can reproduce

asexually, with the use of a vegetative part of the

original plant. This process can occur naturally.

It can also be done manually, and is especiallybeneficial when one wants to create new plants

from fruit or vegetable parent plant. Vegetative

propagation techniques have been used with

varying degrees of success, in attempts to helpdeveloping countries produce larger sources of

food for the population.

http://www.buzzle.com/articles/plants/

http://www.buzzle.com/articles/plants/



• We all are accustomed with growing new

plants from seeds. No doubt, seeds are

one of the most versatile means for

producing new plants. However, the major drawback of seed propagation is that

some species of plants either do not

produce seeds or majority of the seeds arenot viable. In such cases, vegetative

propagation becomes very important.S

van ages o ege a ve



van ages o ege a vePropagation

• The offspring produced are generally

identical, and hence, the more beneficial

characteristics can be preserved.

• In this gardening process only one parent

is required, unlike sexual reproduction

methods like pollination.

• Vegetable propagation is faster.

http://www.buzzle.com/articles/gardening/

http://www.buzzle.com/articles/gardening/



• Many plants produced are able to suffice duringunfavorable conditions. This is due to thepresence of organs which help in asexualreproduction like bulbs and tubers.

• This process of propagation is especiallybeneficial to horticulturists and agriculturists, asthey can raise various fruits and vegetableplants without requiring to buy seeds.

• With modern techniques of tissue culturecombined, one can grow virus free plants.



Cutting Method Of Vegetative

Propagation

• Propagating plants from cuttings method is

also called as striking or cloning, in which

a piece of plant containing at least one

stem cell is placed on suitable medium likesoil, potting mix or rock wool. This cutting

helps to produce new roots, stems or both,

and develops into a new plant.

http://www.buzzle.com/articles/propagating-plants-from-cuttings.html

http://www.buzzle.com/articles/propagating-plants-from-cuttings.html



Stem Cutting

• Stem cuttings can be taken from the main stemor the side branches of the plant. Different typesof stem cuttings are:

• Herbaceous Cutting - Houseplants likechrysanthemum, rhododendron and geranium

are propagated by herbaceous cutting. For thistype, rooting is easy and the growth phase hasnothing to do with root formation. So, you canmake stem cuttings at any time, when the plantis growing actively. More on ways for propagating rhododendron.

http://www.buzzle.com/articles/ways-for-propagating-rhododendrons.html






Stem Cutting

• Softwood Cutting - This cutting is made

from the new stem growth of the current

season and is easy to promote rooting.

Deciduous shrubs like lilac, plum, rose andforsythia are propagated by softwood

cuttings.

http://www.buzzle.com/articles/roses-flowers/

http://www.buzzle.com/articles/roses-flowers/





• Semi-Hardwood Cutting - Broad-leaved

evergreens like azalea, camellia, olive,

citrus and holly are propagated by semi-

hardwood cutting. This method refers tocutting made from the stem growth of the

current season, when the stem is not

completely mature or hard.



• Hardwood Cutting - Over here, the hardstem of the previous year is used for propagation. Hardwood cutting is taken at

a specific time of the year, particularlyduring winter when the plant is inactive or dormant. Deciduous and narrow-leavedevergreens like privet, honeysuckle,

quince, grape, cypress etc. arepropagated by the hardwood cuttingmethod.



Leaf Cuttings

• Leaf cuttings can be made anytime from theplant. A healthy and disease free leaf is cutsmoothly from the plant, which is then used for generating a new plant. Unlike stem cuttings that

require only rooting, both shoot developmentand root formation are necessary in case of leaf cuttings. Not all plants can be propagated bymeans of leaf cutting. Rather we can say

propagation by leaf cutting is successful for afew plants like houseleek, rex begonia andsansevieria.



Root Cutting

• Plant propagation by root cuttings is also limitedto a few species of herbaceous plants, shrubsand bushes and trees. Examples of plants thatcan be propagated by this method include

raspberry, blueberry, globe thistle and acanthus.First, healthy roots of specific size(approximately the diameter of a pencil) areexposed and cut in sections of about 1 ½ - 3inch in length. In order to avoid confusion while

placing the root cutting in growth medium, thefirst top cutting should be made flat and thebottom cutting should be diagonal.

http://www.buzzle.com/articles/shrubs-bushes/






Micropropagation/Tissue Culture

• This method is practiced to multiply a stock plantat a rapid rate, to produce a large number of progeny plants using the modern plant culturemethods. Plant tissue culture encompasses

culturing of plant parts on an artificial medium.The plant parts can be a single cell, tissue or anorgan. It is also referred to as micropropagation.Plant tissue culture was practically implemented

for the first time by Haberlandt, a Germanscientist, in 1902. Later in 1934, Gautheret foundsuccessful results on in-vitro culture of plants.








• The basic key used in plant tissue culture

is the totipotency of plant cells, meaning

that each plant cell has the potential to

regenerate into a complete plant. With thischaracteristic, plant tissue culture is used

to produce genetically identical plants

(clones) in the absence of fertilization,pollination or seeds.

http://www.buzzle.com/articles/plant-cell-structure-and-parts.html

http://www.buzzle.com/articles/plant-cell-structure-and-parts.html






• In plant tissue culture, plants or explants such aspieces of leave, stem or root is cultured in aspecific plant medium, which contains essentialplant nutrients and hormones. Other plant

growth factors like light and temperature aremaintained and regulated by using artificialconditions. All the procedures of plant tissueculture are conducted under sterile (aseptic)

conditions. The explants then develop stem,roots and leaves. The generated plantlets arehardened before planting in outdoor conditions.

http://www.buzzle.com/articles/essential-plant-nutrients.html

http://www.buzzle.com/articles/plant-growth-factors.html




http://www.buzzle.com/articles/essential-plant-nutrients.html






ASEXUAL REPROUCTION IN

ANIMALS



ASEXUAL REPRODUCTION

•Various types of asexual reproduction are:

• Binary fission (animal)

•

Budding (animal)• Fragmentation and segmentation (animal)

• Parthenogenesis (plant, animal)

• Vegetative propagation (natural, plant)

• Vegetative propagation (artificial, plant)

• Sporulation (plant, fungi)



ASEXUAL: BINARY FISSION

• Occurs is protists such as the Amoeba and in bacterial

cells.

• The parent cell splits into two identical daughter cells by

mitosis.

ASEXUAL: BUDDING



ASEXUAL: BUDDING

• Occurs in protists and fungi such as yeast.

• The daughter cell buds or pinches off from the

parent as a smaller replica (clone) then grows to

mature size.

ASEXUAL: FRAGMENTATION and



ASEXUAL: FRAGMENTATION and

SEGMENTATION

• Occurs in flatworms (fragmentation) and ringed

worms (segmentation).

• Parent organism breaks into different fragments or

segments, which form new individuals.

ASEXUAL PARTHENOGENESIS



ASEXUAL: PARTHENOGENESIS

• The growth anddevelopment of anembryo or seedwithout fertilizationby a male.

• Occurs naturally insome lower plants,

some invertebrates(e.g. water fleas,aphids) and somevertebrates (e.g.lizards,salamanders, some

fish, and eventurkeys).

• Parthenogeneticpopulations are

typically all-female.



Fragmentation

• Fragmentation is another form of asexual

reproduction in animals. This is when an

organism is broken into 2 or more pieces,

and each one grows into a new individual.For this type of reproduction the organism

must have good powers of regeneration.



Fragmentation



Fragmentation



Fragmentation

• This could be a disadvantage if the plant is

in poor conditions, as it wouldn't have

good powers of regeneration, and so it

wouldn't be able to reproduce. On thepositive side, it can produce many new

individuals very quickly



Binary Fission

• A method of asexual reproduction that is

employed by most prokaryotes. In binary

fission, the living cell divides into two

equal, or nearly equal, parts. It beginswhen the DNA of the cell is replicated.

http://www.daviddarling.info/encyclopedia/A/asexual_reproduction.html

http://www.daviddarling.info/encyclopedia/P/prokaryote.html

http://www.daviddarling.info/encyclopedia/D/DNA.html

http://www.daviddarling.info/encyclopedia/D/DNA.html

http://www.daviddarling.info/encyclopedia/P/prokaryote.html

http://www.daviddarling.info/encyclopedia/A/asexual_reproduction.html





Binary Fission

• Each circular strand of DNA then attaches

to the plasma membrane. The cell

elongates, causing the two chromosomes

to separate. The plasma membrane theninvaginates (grows inward) and splits the

cell into two daughter cells through a

process called cytokinesis.

http://www.daviddarling.info/encyclopedia/C/chromosome.html

http://www.daviddarling.info/encyclopedia/C/cytokinesis.html

http://www.daviddarling.info/encyclopedia/C/cytokinesis.html

http://www.daviddarling.info/encyclopedia/C/chromosome.html





CLONING

• Cloning is an example of artificial asexual

reproduction.



CLONING



CLONING

Genetic Consequences of




Asexual Reproduction• A consequence of asexual reproduction,

which may have both benefits and costs,

is that offspring are typically genetically

similar to their parent, with as broad arange as that individual receives from one

parent.

• The lack of genetic recombination resultsin fewer genetic alternatives than with

sexual reproduction.


http://www.newworldencyclopedia.org/entry/Genetic_recombination

http://www.newworldencyclopedia.org/entry/Genetic_recombination




Asexual Reproduction Cont`d• Many forms of asexual reproduction, for

example budding or fragmentation,

produce an exact replica of the parent.

This genetic similarity may be beneficial if the genotype is well-suited to a stable

environment, but disadvantageous if the

environment is changing.





Asexual Reproduction Cont`d• For example, if a new predator or

pathogen appears and a genotype is

particularly defenseless against it, an

asexual lineage is more likely to becompletely wiped out by it. In contrast, a

lineage that reproduces sexually has a

higher probability of having more memberssurvive due to the genetic recombination

that produces a novel genotype in each

individual.


http://www.newworldencyclopedia.org/entry/Genotype

http://www.newworldencyclopedia.org/entry/Genotype




Asexual Reproduction Cont`d• Similar arguments apply to changes in the

physical environment. From an

evolutionary standpoint, one could thus

argue that asexual reproduction is inferior because it stifles the potential for change.

However, there is also a significantly

reduced chance of mutation or other complications that can result from the

mixing of genes.

http://www.newworldencyclopedia.org/entry/Evolution

http://www.newworldencyclopedia.org/entry/Mutation

http://www.newworldencyclopedia.org/entry/Mutation

http://www.newworldencyclopedia.org/entry/Evolution



Videos of Asexual Reproduction

• http://www.youtube.com/watch?v=tWfgpH

KP0_4&feature=related

• http://www.youtube.com/watch?v=9moBpp

hvzOI&feature=related

• http://www.youtube.com/watch?v=drcnTg7

ZCoc

http://www.youtube.com/watch?v=tWfgpHKP0_4&feature=related


http://www.youtube.com/watch?v=9moBpphvzOI&feature=related




















Questions & Answers

• Question: What is asexual reproduction?



• Answer: Asexual reproduction involves

only one parent and the offspring is

genetically similar to the parent.



• Question: Name the types of

reproduction that produces genetically

identical offspring?



• Answer: Asexual reproduction is the

type of reproduction that produces

genetically identical offspring.



• Question: What are the different types of

asexual reproduction?



• Answer: The different types of asexual

reproduction are binary fission, budding,

fragmentation, spore formation and

vegetative propagation.



• Question: What is binary fission?



• Answer: When the parent cell dividesinto two cells that are almost identical, it is

called binary fission.





• Which diagram above represents binaryfission?

Asexual Reproduction 2 1

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