Reproductive System of The American Black Bear (female):
Reproduction
The American Black Bear needs to reproduce in order for the species to exponentially grow. Exponential growth is where each generation doubles. They perform sexual reproduction with one male and one female. Both female and male bears have different organs to reproduce. The female reproductive system of The American Black Bear is similar to many other animals. (shown above). Sexual reproduction happens when the gametes conjoin in a process of internal fertilization. The female gametes (sex cells) are eggs, while the male gametes (sex cells) are sperm. Female sex cells are made by oogenesis. Male sex cells are made by spermatogenesis. The egg is in the ovary. When mature the egg goes to the oviduct where fertilization takes place. The egg will develop and grow in the uterus. When sexual reproduction is happening the cervix is where the sperm will enter. While the vagina is very important for sexual reproduction it also keeps bacteria out of the body. The male sperm is made by the testicles. American Black Bears epididymis stores sperm. For sexual reproduction sperm travels from the epididymis through the vas deferens to the prostate to add other liquids. From this semen is made. (1) The scrotal sac (shown below) helps regulate temperature so sperm can exist for sexual reproduction. Black bears mate in May and late June. An interesting fact about Black Bear courtship is the males follow females and they often rest together. (2) Black bears have 74 chromosomes and 37 haploid chromosomes. (3) The bears become sexually mature anywhere from 3-7 years. (4)
(1) http://www.esf.edu/aec/adks/mammals/black_bear.htm
(2) http://www.bear.org/website/bear-pages/black-bear/reproduction/15-courtship-and-mating.html
(3) http://en.wikipedia.org/wiki/List_of_organisms_by_chromosome_count
(4) http://www.michigan.gov/dnr/0,1607,7-153-10363_10856_57530_57536---,00.html
The American Black Bear needs to reproduce in order for the species to exponentially grow. Exponential growth is where each generation doubles. They perform sexual reproduction with one male and one female. Both female and male bears have different organs to reproduce. The female reproductive system of The American Black Bear is similar to many other animals. (shown above). Sexual reproduction happens when the gametes conjoin in a process of internal fertilization. The female gametes (sex cells) are eggs, while the male gametes (sex cells) are sperm. Female sex cells are made by oogenesis. Male sex cells are made by spermatogenesis. The egg is in the ovary. When mature the egg goes to the oviduct where fertilization takes place. The egg will develop and grow in the uterus. When sexual reproduction is happening the cervix is where the sperm will enter. While the vagina is very important for sexual reproduction it also keeps bacteria out of the body. The male sperm is made by the testicles. American Black Bears epididymis stores sperm. For sexual reproduction sperm travels from the epididymis through the vas deferens to the prostate to add other liquids. From this semen is made. (1) The scrotal sac (shown below) helps regulate temperature so sperm can exist for sexual reproduction. Black bears mate in May and late June. An interesting fact about Black Bear courtship is the males follow females and they often rest together. (2) Black bears have 74 chromosomes and 37 haploid chromosomes. (3) The bears become sexually mature anywhere from 3-7 years. (4)
(1) http://www.esf.edu/aec/adks/mammals/black_bear.htm
(2) http://www.bear.org/website/bear-pages/black-bear/reproduction/15-courtship-and-mating.html
(3) http://en.wikipedia.org/wiki/List_of_organisms_by_chromosome_count
(4) http://www.michigan.gov/dnr/0,1607,7-153-10363_10856_57530_57536---,00.html
Reproductive Barriers
There are two types of reproductive barriers: Prezygotic and Postzygotic. Prezygotic is when individuals are physically unable to mate. This might be because of a different number of chromosomes, social pheromones, and reproductive structures such as the female reproductive tract. Postzygotic is when the mating creates a hybrid that don't survive; sterile.
Reproductive System of The American Black Bear (male):
The American Black Bears Mating:
Development
The gestation period for The American Black Bear is 180 days. Most embryo development takes place during the last 6-8 weeks the bear is pregnant. (1) Life expectancy is anywhere from 10-15 years. Females give birth in around December. Cubs are covered in short grey fur when they are born. The cubs eyes are closed for 30-40 days. They start to walk in 40-45 days. (2) In the womb the black bear is a first a zygote (fertilized egg), then a blastocyst, then an embryo, and then a fetus. (3) Females give birth to 1-6 cubs, and there is parental care. (4)
(1) http://www.esf.edu/aec/adks/mammals/black_bear.htm
(2) http://wildpro.twycrosszoo.org/S/0MCarnivor/ursidae/ursus/Ursus_americanus/07Ursus_americanusLifePhys.htm
(3) http://www.michigan.gov/dnr/0,1607,7-153-10363_10856_57530_57536---,00.html
(4) http://www.caveslime.org/kids/cavejourney/SpeciesAccounts/BlackBears.html
The gestation period for The American Black Bear is 180 days. Most embryo development takes place during the last 6-8 weeks the bear is pregnant. (1) Life expectancy is anywhere from 10-15 years. Females give birth in around December. Cubs are covered in short grey fur when they are born. The cubs eyes are closed for 30-40 days. They start to walk in 40-45 days. (2) In the womb the black bear is a first a zygote (fertilized egg), then a blastocyst, then an embryo, and then a fetus. (3) Females give birth to 1-6 cubs, and there is parental care. (4)
(1) http://www.esf.edu/aec/adks/mammals/black_bear.htm
(2) http://wildpro.twycrosszoo.org/S/0MCarnivor/ursidae/ursus/Ursus_americanus/07Ursus_americanusLifePhys.htm
(3) http://www.michigan.gov/dnr/0,1607,7-153-10363_10856_57530_57536---,00.html
(4) http://www.caveslime.org/kids/cavejourney/SpeciesAccounts/BlackBears.html