Asexual and Sexual reproduction

Drawbacks of Sexual Reproduction

Have to find a PARTNER; Have to wait until sexual MATURITY; Not all members of the population REPRODUCE

Benefits of Sexual Reproduction

Sexual reproduction produces a greater chance of variation within a species than asexual reproduction would. This variation improves the chances that a species will adapt to his environment and survive.

Binary Fission

Single-celled organisms (Amoeba, paramecium, euglena) which use asexual reproduction can do so simply by dividing into two equal halves.

Disadvantages Asexual Reproduction

1. No Diversity Since the traits of only one parent is passed on, all of the offspring are exactly identical. This causes for a very big lack of diversity among the population of these organisms. 2. Prone To Extinction All of the same traits also means all of the same weaknesses. Parasites and other predators that have evolved to kill just one of the organisms can take out the entire population. 3. Cannot Adapt An organism has established reactions to certain things, and all of these reactions are passed down to their offspring with asexual reproduction. This makes it impossible for them to adapt to any environment changes.

Benefits of Asexual Reproduction

Allows for rapid reproduction. This means the parent organism will produces the greatest number of offspring for the same nutrients, space, and sunlight; No mates required; Very little / no investment of energy resources

Budding

An offspring grows out of the body of the parent. In yeasts the cell does not divide equally in two halves; instead, there is a large mother cell and a smaller daughter cell.

Sexual vs. Asexual Reproduction

Asexual reproduction results in offspring that are genetically identical to the parent organism. Sexual reproduction results in offspring that are genetically different from the parent organisms.

Methods of asexual reprooduction

Binary fission; Budding; Fragmentation; Parthenogenesis

External Fertilization

External fertilization usually requires a medium such as water, which the sperms can use to swim towards the egg cell. External fertilization usually occur in fish and amphibians. The females lay the eggs in the water and the male squirts the sperm in the same area.

Internal Fertilization

Fertilization occurs within the female. Internal fertilization occurs in mammals, insects, birds, reptiles. Mammals (gorillas, lions, elephants, rats, zebras, and dolphins have live births) Insects, birds, reptiles lay eggs

Fragmentation

In this form, the body of the parent breaks into distinct pieces, each of which can produce an offspring. Some plants can grow from cutting them up and replanting them which is also fragmentation.

Parthenogenesis

Parthenogenesis is a form of asexual reproduction in which females produce eggs that develop without fertilization. Parthenogenesis is seen to occur naturally in some invertebrates, along with several fish, amphibians, and reptiles as well as in many plants. There are no known cases of parthenogenesis in mammals.

Pollination

Pollen is produced in the male organs of the flowers - anthers. Pollination occurs when pollen is transferred from the anthers to the female organs by wind or by animals. If the female stigma is receptive to a pollen grain, the pollen produces a pollen tube, which grows through the female tissue to the egg, where fertilization takes place by the sperm nucleus.

Methods of sexual reproduction

Pollination; External Fertilization; Internal Fertilization

Sexual reproduction

Requiers 2 parents (male & female; sperm & egg) The egg and sperm join (zygote) to form an entirely new organism. Offspring are different from each parent organism because the genes have been combined and shuffled.

Asexual reproduction

Requiers only 1 parent and the offspring are an exact copy of the parent (a clone)

Benifits of Binary Fission

When conditions are good, such as plenty of water, food, right temperatures, etc., binary fission is a very effective way of producing many, many offspring. For example, the cell of a Paramecium can divide, grow, and divide again in the space of 8 hours.