reproduction

Asexual reproduction

• Advantages:

  • Only requires a single individual. 

    • This is beneficial for if there's an organisms that is really rare

    • or if individual is fixed in place

    • enables/enhances ability of animal to colonize new areas 

  • Can produce a large number of offspring quickly 

  • IF environment is stable and predictable, offspring will be adapted 

    • Clones: well adapted to environment that parent is adapted to 

• Disadvantages:

  • Low genetic variation in population

    • Equals missing key prerequisite for natural selection

  • IF environment is changing or unstable.unpredictable low genetic variation reduces chance of natural selection and adaptation 

• Types of asexual reproduction

  • Fission: after a period of growth, organism splits into two

  • Budding: outgrowth of part of a body region of adults organism leading to separation from original organism

  • Fragmentation: breaking of body into two parts with subsequent regeneration 

  • Parthenogenesis: an egg develops into a complete individual with being fertilized (DRAW THE FLOW CHARTS HAPLIOD AND DIPLOID IN ANIMALS)

    • Offspring may be haploid or diploid 

    • Bees-> male drones develop from unfertilized eggs (haploid)

    • Automixis: a type of pathogenesis in which egg replicates all chromosomes or fuses with another egg to produce a diploid individual

Sexual reproduction: production of a new living organism via the combination of genetic information from two individuals 

• Advantages:

  • Offspring have novel combination of genes-> high genetic variation in a population

  • Opportunities for adaptation to changing environment via natural selection 

• Disadvantage:

  • Need a mate

• Reproductive cycles

  • Often influence by changing seasons 

  • Controlled by hormone that are secreted in response to environmental cues

  • Caribou migrate according to day-length 

    • Was timed to match up with new vegetation sprouting in spring

    • Offspring produced in spring when most energy (food) is available

Fertilization: union of egg and sperm (gametes)

• External fertilization: occurs outside the body in a watery environment. Females release eggs into the environment. Males release sperm into the environment. 

  • Needs a watery environment

• Internal fertilization: male delivers sperm directly to female via copulation

  • Cooperate mating behavior 

  • Sophisticated and compatible reproductive system 

  • Does not require a watery environment

  • In many cases females can store sperm for later 

Sex determination in animals:

• Sex: type of gamete an organisms is capable of producing 

  • Males: produce small motile (movable/can move) gamete (sperm has flagella to move)

  • Females: produce large, sessile (does not move itself) gametes (egg doesn’t have a flagella

  • Hermaphrodites: capable of producing both gamete types

    • Can be sequential (i.e. changing sex)

• How is sex determined in animals?

  • genetic/chromosomes 

    • Birds and mammals have a set of sex chromosomes which have genes that control gonad development 

      • Gonad: organisms which produce egg or sperm 

        • Egg=ovary

        • sperm=testes

        • XX is female

        • XY is male

  • Temperature dependent sex determination (TSD)

    • Common in reptiles, eggs are in a nest underground

    • Embryo develop as male or female depending on the temperature at which they incubate