Mammals reproduce sexually, via the union of sperm and egg cells. Except for five species of egg-laying mammals, called monotremes, all mammals give birth to live young.Continue Reading
Mammals possess two main types of cells: somatic cells and sex cells. Somatic cells account for most of the body's cells and are responsible for growth, repair and healing. Sperm and egg sex cells contain one set of chromosomes each and fuse during sexual reproduction to form a zygote that later develops into an embryo and then a fetus. In most mammals, the fetus develops in the uterus until it is able to survive outside the mother's body. In the pouched mammals, called marsupials, offspring are born very early and finish development in the female's pouch. A placenta forms in some species of marsupials, while a simple yolk sac delivers vital nutrients in others.
Five species of mammals, called monotremes, actually lay eggs. Monotremes, including the duck-billed platypus and four species of echidna, are all native to Australia and New Guinea. Like birds, monotremes possess a cloaca, which is a single orifice that serves for both reproduction and excretion. The eggs receive nourishment from the female's body for a few weeks before they are laid. Like other mammals, monotremes have mammary glands and feed their young milk.Learn more about Animal Reproduction
Haploid numbers refer to the number of chromosomes in an egg or sperm cell, and it has the abbreviation "n." Diploid numbers refer to the number of chromosomes in other types of cells, such as the zygote that appears when the sperm cell fertilizes an egg, abbreviated "2n."Full Answer >
Zebras reproduce sexually: The male zebra, which is called a stallion, mounts a female zebra, which is called a mare, and deposits sperm in the mare's vagina via the stallion's penis. If the mating is successful, the mare births a single foal 12 to 13 months later.Full Answer >
Arthropods reproduce by transferring sperm from the male to a female by way of sealed packets called spermatophores, according to the Encyclopedia Britannica. With few exceptions, arthropods are sexed as male or female, and both sexes have gonads, or sex organs, directly connected to ducts on the ventral surface of their trunks. The exact location of these ducts varies considerably amongst arthropod species.Full Answer >
Platyhelminthes, also known as flatworms, are hermaphrodites, meaning individuals of the species produce both sperm and eggs. These are released from the platyhelminthes where they become cross-fertilized by other platyhelminthes. Two types of platyhelminthes, trematoda and cestoda, lay eggs constantly. The turbellarian class has a seasonal cycle. Turbellaria also reproduce asexually by dividing. Turbellaria are the only class able to regenerate body parts.Full Answer >