animal reproduction ppt
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Animal ReproductionBy: Madison Allen
Asexual vs. Sexual Reproduction
In sexual reproduction, the fusion of haploid gametes forms a diploid cell, the zygote. The animal that develops from a zygote can in turn give rise to gametes by meiosis. The female gamete, the egg, is a large, nonmotile cell. The male gamete, the sperm, is generally a much smaller, motile cell.
Asexual reproduction is the generation of new individuals without the fusion of egg and sperm. In most asexual animals, reproduction relies entirely on mitotic cell division.
Asexual Reproduction
Many invertebrates can reproduce asexually by fission, the separation of a parent organism into two individuals of approximately equal size.
Also common among invertebrates is budding, in which new individuals arise from outgrowths of existing ones. ◦Ex. In certain species of coral and hydra, new
individuals grow out from the parents body.Parthenogenesis is a form of asexual
reproduction in which an egg develops without being fertilized.
Asexual Reproduction
Sexual Reproduction
The vast majority of eukaryotic species reproduce sexually.
Most animals exhibit cycles in reproductive activity, often related to changing seasons. In this way, animals conserve resources, reproducing only when sufficient energy sources are available and when environmental conditions favor the survival of offspring. ◦ For example, ewes (female sheep) have a reproductive
cycle lasting 15-17 days. Ovulation is the release of mature eggs and occurs
at the midpoint of each cycle. Reproductive cycles are controlled by hormones,
which in turn are regulated by environmental cues. ◦ Common environmental cues are changes in day length,
seasonal temperature, rainfall, and lunar cycles.
Sexual Reproduction
Sexual Reproduction Continued
Hermaphrodism is when each individual has both male and female reproductive systems. Because each hermaphrodite produces as both male and female, any two individuals can mate. ◦This is present in stationary animals, such as
barnacles, burrowing animals, such as clams, and some parasites, such as tapeworms.
External vs. Internal Fertilization
Fertilization is the union of sperm and egg, which can be either external or internal.
External fertilization – the female releases eggs into the environment, where the male fertilizes them
Internal fertilization – sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
External
Internal
Reproductive Organs
In many insect species, the female reproductive system includes a spermatheca, a sac in which sperm may be stored for extended periods, a year or more in some species.
In many nonmammalian vertebrates, the digestive, excretory, and reproductive systems have a common opening to the outside, the cloaca.
Female Reproductive Organs
Ovaries – the female gonads are a pair of ovaries that border the uterus and are held in place in the abdominal cavity by ligaments (ovaries produce eggs and reproductive hormones)
Uterus – where eggs are fertilized and development of the young occurs
Female Reproductive Organs
Male Reproductive Organs
Testes – consists of many highly coiled tubes surrounded by several layers of connective tissue, this is where the sperm is formed
Male Reproductive Organs
Spermatogenesis
Spermatogenesis – the formation and development of sperm, is continuous and prolific in adult males
Oogenesis
Oogenesis – the development of mature eggs, is a prolonged process in the human female
Conception and Birth
Human gestation is divided into three trimesters of about three months each. ◦First, Second, and Third Trimester
Placenta – a structure in the pregnant uterus for nourishing a viviparous fetus with mother’s blood supply; formed from the uterine lining and embryonic membranes
Labor – the process by which childbirth occurs; a series of strong, rhythmic uterine contractions
Of course, protection is always an option ;)