Gametes are also known as reproductive cells which contains only half the amount of DNA or half number of chromosomes as compared to the normal body cells of an organism.
The Sexual reproduction has many advantages over asexual reproduction. In asexual reproduction, the offspring produced is almost identical to their parent because of same genes. So, much genetic variation is not possible. This is a disadvantage as it inhibits the further evolution of the organism. In Sexual reproduction the offsprings although similar to their parents, are not identical to them or to one another. Because the offsprings receive some genes from the mother and some from the father.
So, mixing of genes makes various different combinations and so all the offsprings have genetic variations. As humans, we are used to thinking of animals as having two separate sexes, male and female, determined at conception. However, in the animal kingdom, there are many variations on this theme.
Hermaphroditism occurs in animals where one individual has both male and female reproductive parts. Invertebrates, such as earthworms, slugs, tapeworms and snails, are often hermaphroditic. Hermaphrodites may self-fertilize or may mate with another of their species, fertilizing each other and both producing offspring. Self fertilization is common in animals that have limited mobility or are not motile, such as barnacles and clams.
Learning Objectives Discuss sexual and asexual reproduction methods. Key Points Asexual reproduction includes fission, budding, fragmentation, and parthenogenesis, while sexual reproduction is achieved through the combination of reproductive cells from two individuals. The ability of a species to reproduce through fragmentation depends on the size of part that breaks off, while in binary fission, an individual splits off and forms two individuals of the same size.
Budding may lead to the production of a completely new adult that forms away from the original body or may remain attached to the original body. Observed in invertebrates and some vertebrates, parthenogenesis produce offspring that may be either haploid or diploid. Sexual reproduction, the production of an offspring with a new combination of genes, may also involve hermaphroditism in which an organism can self-fertilize or mate with another individual of the same species.
Key Terms binary fission : the process whereby a cell divides asexually to produce two daughter cells hermaphroditism : having sexual organs of both sexes parthenogenesis : a form of asexual reproduction where growth and development of embryos occur without fertilization. In some crocodiles, moderate temperatures produce males, while both warm and cool temperatures produce females.
In some species, sex is both genetic- and temperature-dependent. Individuals of some species change their sex during their lives, alternating between male and female. Privacy Policy. Skip to main content. Animal Reproduction and Development. Search for:. Reproduction Methods. Methods of Reproducing Animal reproduction is essential to the survival of a species; it can occur through either asexual or sexual means. Learning Objectives Describe reproduction in animals.
Asexual reproduction yields genetically-identical organisms because an individual reproduces without another. In sexual reproduction, the genetic material of two individuals from the same species combines to produce genetically-different offspring; this ensures mixing of the gene pool of the species.
Organisms that reproduce through asexual reproduction tend to grow exponentially and rely on mutations for DNA variation, while those that reproduce sexually yield a smaller number of offspring, but have larger genetic variation. Key Terms reproduction : the act of producing new individuals biologically clone : a living organism produced asexually from a single ancestor, to which it is genetically identical.
Types of Sexual and Asexual Reproduction Asexual and sexual reproduction, two methods of reproduction among animals, produce offspring that are clones or genetically unique. Learning Objectives Discuss sexual and asexual reproduction methods. Key Takeaways Key Points Asexual reproduction includes fission, budding, fragmentation, and parthenogenesis, while sexual reproduction is achieved through the combination of reproductive cells from two individuals.
The ability of a species to reproduce through fragmentation depends on the size of part that breaks off, while in binary fission, an individual splits off and forms two individuals of the same size. Budding may lead to the production of a completely new adult that forms away from the original body or may remain attached to the original body. Observed in invertebrates and some vertebrates, parthenogenesis produce offspring that may be either haploid or diploid.
Sexual reproduction, the production of an offspring with a new combination of genes, may also involve hermaphroditism in which an organism can self-fertilize or mate with another individual of the same species. Key Terms binary fission : the process whereby a cell divides asexually to produce two daughter cells hermaphroditism : having sexual organs of both sexes parthenogenesis : a form of asexual reproduction where growth and development of embryos occur without fertilization.
Sex Determination Sex determination in animals may be regulated by the presence of chromosomes or through the impact of an environmental factor. Learning Objectives Differentiate among the various ways animals determine the sex of offspring. Key Takeaways Key Points Mammals, birds, and some other animal species depend on heterozygous or homozygous chromosome combinations for sex determination. Cool or warm temperatures affect sex determination in species such as crocodiles and turtles.
A single individual can produce offspring asexually and large numbers of offspring can be produced quickly; these are two advantages that asexually reproducing organisms have over sexually reproducing organisms.
In a stable or predictable environment, asexual reproduction is an effective means of reproduction because all the offspring will be adapted to that environment.
In an unstable or unpredictable environment, species that reproduce asexually may be at a disadvantage because all the offspring are genetically identical and may not be adapted to different conditions. During sexual reproduction, the genetic material of two individuals is combined to produce genetically diverse offspring that differ from their parents. The genetic diversity of sexually produced offspring is thought to give sexually reproducing individuals greater fitness because more of their offspring may survive and reproduce in an unpredictable or changing environment.
Species that reproduce sexually and have separate sexes must maintain two different types of individuals, males and females. Only half the population females can produce the offspring, so fewer offspring will be produced when compared to asexual reproduction. This is a disadvantage of sexual reproduction compared to asexual reproduction.
Asexual reproduction occurs in prokaryotic microorganisms bacteria and archaea and in many eukaryotic, single-celled and multi-celled organisms.
There are several ways that animals reproduce asexually, the details of which vary among individual species. Fission, also called binary fission, occurs in some invertebrate, multi-celled organisms. It is in some ways analogous to the process of binary fission of single-celled prokaryotic organisms. The term fission is applied to instances in which an organism appears to split itself into two parts and, if necessary, regenerate the missing parts of each new organism.
For example, species of turbellarian flatworms commonly called the planarians, such as Dugesia dorotocephala , are able to separate their bodies into head and tail regions and then regenerate the missing half in each of the two new organisms. Sea anemones Cnidaria , such as species of the genus Anthopleura Figure Budding occurs commonly in some invertebrate animals such as hydras and corals. In hydras, a bud forms that develops into an adult and breaks away from the main body Figure View this video to see a hydra budding.
Fragmentation is the breaking of an individual into parts followed by regeneration. If the animal is capable of fragmentation, and the parts are big enough, a separate individual will regrow from each part. Fragmentation may occur through accidental damage, damage from predators, or as a natural form of reproduction. Reproduction through fragmentation is observed in sponges, some cnidarians, turbellarians, echinoderms, and annelids.
In some sea stars, a new individual can be regenerated from a broken arm and a piece of the central disc. This sea star Figure Fisheries workers have been known to try to kill the sea stars eating their clam or oyster beds by cutting them in half and throwing them back into the ocean. Unfortunately for the workers, the two parts can each regenerate a new half, resulting in twice as many sea stars to prey upon the oysters and clams.
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