Species difference in reproduction Flashcards
species
Individuals of the same species can reproduce to produce offspring of the same species. Two individuals belonging to different species normally cannot produce viable offspring or only produce offspring that is sterile.
reproduction
Biological process by which new individual organisms are produced from their parents = offspring
species differences in reproduction
Asexual vs Sexual Reproduction
Oviparity - Viviparity -Oviviparity
External vs Internal Fertilization
asexual reproduction
Offspring originates from a single organisms and inherits the parents’ genes
- Asexual reproduction main reproduction form for most single-celled organisms like eubacteria, protists, and archae bacteria
- Most fungi and plants are also reproducing asexually
- All prokaryotes reproducing asexually without fusion and formation of gametes
gemmation
Formation of small buds on the surface of the progenitor which can develop into a new individual
- Eg hydra
fragmentation
A new organism is growing from fragments of the progenitor
- Eg flatworm
advantages and disadvantages of asexual repro
Advantages:
- Speed, no gamete formation necessary – very quick
- Advantage for small populations e.g. in secluded areas
- Not very complex, requires less energy compared to sexual reproduction
- Advantage in stable environment
Disadvantages:
- Offspring is clone of parent –> little genetic diversity
- Environment usually not stable long term -> want to have diversity to be able to adapt to different environments
- Often struggle for existence as well as overcrowding
sexual reproduction
Consists of gamete formation, fertilisation and development of the zygote
Gametes:
- Haploid chromosome set
- Spermatozoa: produced in male testicles
- Ova: produced in female ovaries
- Fertilization and zygote (diploid chromosome set) –> Embryo –> Fetus
advantages and disadvantages of sexual repro
Advantages:
- Advantage for introducing genetic diversity
- Advantage in a changing environment
Disadvantages:
- Cost intensive – a lot of energy
- Only 50% of the genome contribute to the offspring
- Fewer offspring
- Sharing of beneficial genes
oviparity
- Fertilized eggs laid outside the female’s body and develop there
- No subsequent protection or nourishment
- Embryo receives nourishment from the yolk that is a part of the egg
o Most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds
viviparity
- Fertilized eggs are retained inside the female
- Eggs lack hard outer covering or shell
- Embryo receives nourishment from the mother’s blood through a placenta or delivered as uterine milk
- Offspring develops in the female and is born alive
o Occurs in most mammals, some cartilaginous fish, and a few reptiles
ovoviparity
- Eggs are fertilized then retained inside the female’s body
- Embryos do not receive direct nourishment from the mother
- Embryo receives nourishment from the egg’s yolk
- Young are fully developed when they are hatched
o Some bony fish, some sharks, some lizards, some snakes, some vipers, and some invertebrate animals
external vs internal fertilisation
- External fertilization: Male and female’s gametes unite outside the female’s body
- Internal Fertilization: Male deposits his sperm directly into the female’s body
external Fert
usually occurs in aquatic env, both eggs and sperm are released into the water = spawning
- Water protects the eggs from drying out during development
- Gametes have to be released at the same time and in the same location to increase the likelihood of fertilization
o water temperature
o length of daylight
o moonlight important external stimulus
o pheromone cues
o Individual males court individual females to release the eggs, at which point the male releases the sperm near these –e.g. amphibians
internal fert
- Internal fertilization of land-based animals
- Advantage of protecting the fertilized egg from dehydration on land
- Increases the likelihood of fertilization by a specific male
- Fewer offspring produced, but their survival rate is higher
- Often embryo isolated within the female, which limits predation on young
- Specific individuals are chosen for mating = sexual selection
sexual selection
- Type of natural selection where one sex has a preference for certain characteristics in individuals
- In most sexually reproducing species females select traits in males
o males compete with each other for access to females for mating - Sexual selection often leads to sexual dimorphism
o differences in size or appearance between males and females
o secondary sexual characteristics e.g. pronounced colaoration, increased size
animal mating systems
- Instead of (or in addition to) competing directly with each other to have the opportunity to mate with a female, males can also compete for fertilization of a female’s eggs after mating has already occurred!
- Competing after mating = indirect male competition = sperm competition ->results in one male being more successful than another at fertilizing a female’s eggs o Mate guarding o Copulatory plugs o Elaborate penis morphology o Large quantity of semen
first male advantage
- Mate guarding: Male remains close by the female after mating –> prevents other males from mating with her until there has been time for his sperm to fertilize the eggs
- Copulatory plugs: Sticky residue in male’s ejaculate –> temporarily blocks entry to the female’s reproductive tract –> physically prevents other males to mate with her
o Allowing time for the first male’s sperm to fertilize the eggs
second male advantage
- Elaborate penis morphology: Can help to remove the sperm of previous males from the female’s reproductive
- Large quantity of semen: Large volume of ejaculate helps to flush out the sperm deposited in the female’s reproductive tract by the previous male
o Large ejaculate volume –> testes must also be large
species different in repro tracts (baculum)
- Most non-human male mammals have a penis which is stored internally until erect & a penis bone = baculum
Baculum
- Extra-skeletal bone not attached to the rest of the skeleton
- Baculum kept in the male’s abdomen, when required, abdominal muscles push penis bone out into the penis causing an erection
- Helps males maintain an erection long enough to penetrate a female’s reproductive tract and deliver sperm
- Advantage of speed - mating often has to be quick and opportunistic
- Most primate males have a baculum, also cats, dogs and rats
- humans don’t have
marsupials
- Female has two (or 3) vaginas - both open externally through one orifice but lead to different compartments within the uterus
- Males usually have a two-pronged penis, corresponding to the females’ two vaginas
- Marsupials typically develop their offspring in an external pouch containing teats
- Males have prostate and bulbourethral gland but not seminal vesicles
species difference in reproductive tracts
- Only one body opening
- Cloaca is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts
- All amphibians, birds, reptiles, have this combined orifice to excrete both urine and feces
- Birds reproduce using their cloaca
o Cloacal kiss – cloaca male to cloaca female
o In some birds, males have a phallus
Chicken
- Reproductive tract of a chicken
- Yellow orbs on the left are the ova with developing yolk in the ovary –> the bigger ones will be released first
- The magnum is larger and adds albumen
- The isthmus is narrower and adds the membranes
- Guess what the shell gland does? The finished eggs exit via the vent
