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Asexual reproduction

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A method of reproduction with all the genetic information coming from one parent.

Humans, and most animals, reproduce sexually. Why would some forms of life reproduce asexually?

There are advantages and disadvantages

Advantages of asexual reproduction

1. Can quickly produce large quantities of offspring.

This helps to fill up niche’s quickly and prevent intruders and competition from invading.

2. No mate required

3. Some species can reproduce sexually, but if unable to find a mate, can reproduce asexually.

4. No investment needed to take care of offspring (“children.”)

5. All children are clones (like identical twins.) So if the parent is well-adapted to the environment, then the offspring will be as well.

Disdvantages of asexual reproduction

Very little genetic variation. Above, that was phrased as a positive (“if the parent is well-adapted to the environment, then the offspring will be as well.”) But this can be a negative as well. If the environment changes, then most of the offspring may not be able to survive. This makes the species more prone to extinction.

Genetic changes only come from sexual reproduction; this allows some percent of the offspring to be more likely to be able to survive changes in the environment.

Many methods

1.  binary fission –the parent organism is replaced by two daughter organisms, because it literally divides in two.

Examples: Bacteria, Archaea, and many protists (single celled organisms like amoebas)

amoeba fission asexual.png

2.  budding — involves one parent dividing its nucleus equally, but the cytoplasm divides unequally, e.g. yeast.

Yeast budding asexual

from byjus.com/biology/budding

3.  sporulation (spore formation) – Reproduction involving specialized single cells, coming from one parent.e.g. mold spores

bread mold spores

4. Vegetative reproduction is when a new plant grows from a fragment of the parent plant. It can occur naturally or be induced by horticulturists.

Although most plants normally reproduce sexually, many have the ability for vegetative propagation

vegetative reproduction

from leavingbio.net/vegetative-propagation

and

Layering vegetative reproduction

5. Hydra can reproduce asexually, by budding, or sexually.

When food is plentiful, many Hydra reproduce asexually by producing buds in the body wall, which grow to be miniature adults and break away when they are mature.

budding-asexual-reproduction-in-hydra

When conditions are harsh, often before winter or in poor feeding conditions, sexual reproduction occurs in some Hydra. Swellings in the body wall develop into either an ovary or testes. The testes release free-swimming gametes into the water, and these can fertilize the egg in the ovary of another individual. (Wikipedia)

Asexual repro uses mitosis

Key Results of Mitosis: The same chromosome number is retained from generation to generation. Each daughter cell receives an exact copy of the chromosomes of the parent cell.  (clones)

Resources

asexual reproduction: eschooltoday

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

8.MS-LS3-2. Construct an argument based on evidence for how asexual reproduction results in offspring with identical genetic information and sexual reproduction results in
offspring with genetic variation. Compare and contrast advantages and disadvantages
of asexual and sexual reproduction.

College Board Standards for College Success: Science

Standard LS.5 Information Transmission, Storage and Retrieval
Living systems have multiple mechanisms that are used to store, retrieve and transmit information.

LS.5.2 Genetic Information Transmission
Students understand that during reproduction, genetic information (DNA) is transmitted between parent and offspring. In asexual reproduction the lone parent contributes DNA to the offspring, and in sexual reproduction both parents contribute DNA to the offspring.

LSM-PE.5.2.4 Explain and justify, using representations, why the DNA of the daughter cells of asexually reproducing organisms are identical to the DNA of parent cells. Explanation and justification are based on knowledge of the mechanisms (e.g., asexual reproduction, DNA replication) of DNA transmission from generation to generation in asexually reproducing organisms.

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