chapter 9 - reproduction Flashcards
unit 2 aos 2
genetic diversity of a population
the amount of genetic variation
gene pool
the sum of all the different genes and alleles that are present in a population and species
-influenced and maintained by a number of naturally occurring mechanisms
why is genetic diversity important?
-protects longevity of species by guarding against disadvantageous environmental changes
-larger the gene pool, greater the resilience to environmental change
-populations with more alleles are more likely to have alleles that are already adapted to new environment
sexual reproduction
-involves fusion of two haploid gametes to form a single, genetically unique, diploid zygote
oviparity
-eggs are released into the external environment, where the embryo develops
-occurs in frogs, snakes, lizards, hens, ducks etc
viviparity
-embryo develops inside mother’s body and is born after a period of gestation
-occurs in humans, bears, giraffes, cattle, salamanders etc
reproduction of angiosperms (pollination)
-pollen is collected by stigma of flower and fuses with ovule
-embryo that develops will become a seed
-occurs in plants
advantages of sexual reproduction
-increases genetic diversity by allowing for recombinant offspring
-improving genetic resistance by promoting presence of different alleles
-combining genetic material reduces chances of offspring inheriting genetic disorder
disadvantages of sexual reproduction
-cost of male progeny
-time, energy, and resources required to attract and find a mate
-risk of stds
-risk of losing offspring to outside influences
asexual reproduction
-offspring/daughter cells are clones of each other and of parent
types of asexual reproduction
-binary fission
-budding
-fragmentation
-vegetative propagation
-sporogenesis
-parthenogenesis
binary fission
-one organism divides into two identical organisms
-occurs in simple prokaryotic organisms
budding
-involves formation of a bud, which forms due to increased cell growth, then breaks away from main organism, where it can develop into separate organism
-occurs in yeast, sponges, jellyfish, coral, worms
fragmentation
-involves parent organism breaking into separate fragments, each of which is capable into developing in separate organism
-occurs in simple eukaryotes (worms? and starfish) and many plant species
vegetative propagation
-allows a plant to reproduce without seeds
-part of plant breaks away from original plant, then independently grows into new plant
sporogenesis
-involves formation of spores (found on surface on organisms), which are dispersed into the surroundings where they grow into larger organisms
-occurs in many plants, fungi, algae, moulds
parthenogenesis
-an embryo can develop from a female gamete alone
-results in eggs produced via mitosis and develop into organism identical to female parent
-rare and occurs in less than 0.1% of all vertebrate species
advantages of asexual reproduction
-populations grow faster than sexually reproducing ones
-offspring identical to parent - important as organism’s phenotype is fine-tuned to survive environment
-doesn’t require mate
-requires little parental investment
disadvantages of asexual reproduction
-genetic diversity is low, populations may suffer from rapid environmental change
reproductive cloning in animals
-somatic cell transfer
-embryo splitting
somatic cell transfer (scnt)
-involves donated egg cells and donated somatic cell
-offspring is genetically identical to donated somatic cell
steps of scnt
- enucleation - removal/destruction of nucleus from donated egg cell to produce an enucleated egg cell
- extraction - donated somatic cell’s nucleus is extracted
- insertion - somatic cell’s nucleus is inserted into enucleated egg cell
- development - cell begins to divide and develop into an embryo, which is implanted into a surrogate mother
applications of scnt
-has been used to clone living and recently deceased animals
-dolly the sheep in 1997
complications of scnt
-animal suffering
-human cloning - illegal in many countries
-premature aging
