The Importance Of Reproductive Success
The importance of reproductive success is to continue the growth of a species, which is the main objective of any organism. The survival of the species depends on reproductive success. Asexual reproduction is when there is only one parent is involved and the offspring is a clone of the parent. There are four types of asexual reproduction: binary fission, budding, fragmentation, and vegetative propagation. Binary fission is cell division that happens in prokaryotes (bacteria). DNA is doubled and the cells divide. Budding is a form of asexual reproduction where the offspring branches are grows from the parent. Hyrdras produce by budding. Fragmentation or regeneration is when a piece of the organism forms a new organism (ex. starfish, sponges). Vegetative propagation happens in strawberries, where a root of the plants grows up to the surface the soil to form a new plant. Sexual reproduction involves two parents. Traits are shuffled to make genetically varied offspring, in other words not clones.
There are two ways cells divide and reproduce: mitosis and meiosis. Mitosis is a process of asexual reproduction where a cell divides producing a second cell that is an exact copy of the original. The cell that is produced is a diploid cell, which means the cell has a full set of chromosomes (46 chromosomes). Mitosis occurs in all organisms and is used mainly to grow and repair the body. Meiosis is another type of cellular reproduction that produces sex cells or gametes. Meiosis results in four haploid cells (23 chromosomes), however in females only one of the eggs that is produced survives. In meiosis the resulting cells are genetically variable. |
Great Blue Heron Reproduction
Herons, like all birds do not have live births, they have eggs with they incubate in a nest for 27-29 days before they hatch. The breeding for Great Blue Herons is usually from March to May in the north and in the south it's usually from November to April. The females lay 2-7 eggs and both parents take part in incubating them. Incubation is the process of keeping the egg warm so the baby is protected while it's developing. The eggs hatch after 26-30 days. Babies live in the nest for about two months before they are able to live on their own. Herons become sexually mature at 22 months.
Male birds have a pair of testes that shrink a considerable amount during non breeding, but during breeding season they expand to be 100 times larger. Sperm cells of birds cannot develop at high temperatures so many birds have a massive drop in body temperature at night. Other birds have a swelling of the vas deferens tube which connects the testes to the cloaca, which is similar to the scrotum of mammals. Copulation occurs by what is called a "cloacal kiss", with the male on top of the female with his tail twisting under the female. They rub their cloacas together to transfer sperm and fertilize the eggs within the female. The eggs are held within the ovaries, like in humans. The ovary of a mature female bird may contain about 4,000 ova (eggs). These eggs can develop into yolks. Yolks contain protein, fats and lipids that are produced in the liver and flow through the bloodstream to the maturing egg (ovum). The yolk contains a single ovum cell which when fertilized, turns into a chick. The oviduct is a coiled tube in the female which develops all parts of the egg except the yolk. Like in humans, when the hormone LH is released from the brain, the sac holding the egg breaks and ovulation occurs. In birds the egg is then released into the infundibulum, a part of the oviduct, which is where fertilization can take place. After fertilization the egg travels to the magnum area of the oviduct and the egg white is added. The egg white is similar to the placenta in that is feeds the developing embryo. The eggs continues to travel down into the isthmus region of the oviduct where the protective shell membrane is added to the egg. The egg then goes to the uterus where it spends 20 hours. Water and salt are added to the egg as well as the inner, middle and outer layer of the shell. The egg then travels to the vagina where a coating is added to the egg to protect it from harmful bacteria. The eggs is then transferred to the cloaca and is laid.
Male birds have a pair of testes that shrink a considerable amount during non breeding, but during breeding season they expand to be 100 times larger. Sperm cells of birds cannot develop at high temperatures so many birds have a massive drop in body temperature at night. Other birds have a swelling of the vas deferens tube which connects the testes to the cloaca, which is similar to the scrotum of mammals. Copulation occurs by what is called a "cloacal kiss", with the male on top of the female with his tail twisting under the female. They rub their cloacas together to transfer sperm and fertilize the eggs within the female. The eggs are held within the ovaries, like in humans. The ovary of a mature female bird may contain about 4,000 ova (eggs). These eggs can develop into yolks. Yolks contain protein, fats and lipids that are produced in the liver and flow through the bloodstream to the maturing egg (ovum). The yolk contains a single ovum cell which when fertilized, turns into a chick. The oviduct is a coiled tube in the female which develops all parts of the egg except the yolk. Like in humans, when the hormone LH is released from the brain, the sac holding the egg breaks and ovulation occurs. In birds the egg is then released into the infundibulum, a part of the oviduct, which is where fertilization can take place. After fertilization the egg travels to the magnum area of the oviduct and the egg white is added. The egg white is similar to the placenta in that is feeds the developing embryo. The eggs continues to travel down into the isthmus region of the oviduct where the protective shell membrane is added to the egg. The egg then goes to the uterus where it spends 20 hours. Water and salt are added to the egg as well as the inner, middle and outer layer of the shell. The egg then travels to the vagina where a coating is added to the egg to protect it from harmful bacteria. The eggs is then transferred to the cloaca and is laid.