5. Reproduction.pdf

Reproduction Aarni Auerniitty Asexual reproduction  Production of clones  all individuals are genetically identical  New individual is born from a single cell or a part of the ‘mother’  Common amongst single celled organisms, plants and fungi for example  Different ways:  Bi...

Reproduction Aarni Auerniitty Asexual reproduction  Production of clones  all individuals are genetically identical  New individual is born from a single cell or a part of the ‘mother’  Common amongst single celled organisms, plants and fungi for example  Different ways:  Binary fission (jakautuminen)  Multiplication (monistuminen)  Budding (silmikoituminen/kuroutuminen)  Spores (itiöt)  Runners (rönsyt), rhizomes (maavarret), root sprouts (juurivesat)  Regeneration Parthenogenesis  New individual is developed from a single egg cell without fertilisation  Most common in colony forming insects and other invertebrates  More efficient, no males needed Sexual reproduction  Reproduction through merging of gametes  new individuals are a mix of the genes of the parents  genetic diversity  Sperm cells, pollen  Egg cells  Unisexuals or hermaphrodites  Most organisms are unisexual = they produce only sperm or egg cells  Hermaphrodites produce both sperm and egg cells and have both sex organs e.g. earthworms  Insemination  Internal or external fertilization  Some animals have courting behaviour  Often female choice over competing males  https://www.youtube.com/watch?v=rX40mBb8bkU  https://www.youtube.com/watch?v=ZPFkmwo8DQU  Meiosis  Meiosis (right) = nuclear division of gametes  Instead of two identical cells like in mitosis (below), four unique cells are born with half of the chromosome count Comparison Asexual Sexual  No need to find a mate  More genetic variety  No courting  Faster evolution  Efficient --> less resources used  Easier to adapt to changes  Quick population growth  Takes more time and resources  More offspring  Need to find a mate  Easy to spread to new areas  Less offspring  Little genetic diversity  More common to take care of the offspring  Struggle in changing environment  Reproduction strategies  K-strategists  Few offspring  Cared by parents  Most survive to reproduce  E.g. top predators  R-strategists  A lot of offspring  Offspring not cared for  Most die and only a few survive to reproduce  E.g. many fishes  Many species between the two extremes Life cycles  Jellyfish  Alters between sexual and asexual reproduction  Parasites  Often complex life cycles involving several hosts