46 Animal Reproduction Flashcards
What forms of asexual reproduction are seen in animals?
Fission, budding, fragmentation and parthenogenesis, Also a special form used by sea sponges
What is fission in terms of animal asexual reproduction?
When one animal divides into two genetically identical offspring.
What is an example of an animal that undergoes fission?
Sea anemones
What is budding in terms of animal asexual reproduction?
When the genetically identical child growths as an offshoot of the parent.
Does asexual reproduction occur in vertebrates?
Yes, in a few species such as the “whiptail lizard”
What is an example of an animal that undergoes budding?
“Stony corals” although the offspring do not detach from the parent, resulting in a colony forming.
What is the special form of asexual reproduction performed by sea sponges?
They release specialised groups of cells that can grow into new individuals.
What is fragmentation in terms of asexual reproduction?
The body breaks into multiple pieces, all of which grow (known as “regeneration”) into individual organisms
What are some examples of animals that perform “fragmentation and regeneration”?
Many sponges, cnidarians bristle worms and sea squirts.
What is “parthogenesis”?
A form of asexual reproduction in which the offspring develops from an unfertilised egg.
What are some examples of animals that perform parthogenesis?
Bees, wasps and ants. Also occasionally in Komodo dragons and hammerhead sharks.
In terms of haploidy, what happens to offspring produced through parthogenesis?
Some, such as male honeybees (drones), develop into haploid adults.
Others are diploid, such as the fertile queen.
Are haploid offspring produced through “parthogenesis” fertile?
They can be and simply produce gametes without meiosis.
Through what principle is asexual reproduction beneficial?
The “two-fold cost of sex” principle
What is the “two-fold cost of sex”
In asexual populations all of the offspring can produce offspring, and thus the size of the population double with each generation (if two offspring per parent)
In sexual populations only half of the offspring can give birth (the females). If each couple has 2 children then on average the population size will not increase.
Therefore asexual populations will theoretically always increase in size faster than sexual populations.
What is “ovulation” broadly speaking?
The cyclical release of mature eggs.
What do “reproductive cycles” include?
Ovulation and also seasonal cycle i.e. increased fertility during autumn.
Why are seasonal “reproductive cycles” important?
If, for example a sheep is most fertile in autumn, its babies will be born in spring.
Thus their will be plentiful vegetation and warm temperatures.
How are seasonal “reproductive cycles” regulated?
Typically day length.
What is an example of an animal that performs both asexual and sexual reproduction? What specific advantage does this yield?
The water flea (Daphnia) produces parthogenic eggs (asexual reproduction) when conditions are good and produces eggs sexually when conditions are not favourable.
In this way the flea rapidly produces new offspring when the conditions are favourable i.e. summer. When the conditions are less favourable, and rapid population growth would not be sustainable, the Daphnia exploit the advantages of sexual reproduction.
What does “hermaphroditism” mean?
When one individual has both male and female reproductive organs.
How do pathogenic offspring become diploid?
Through chromosome doubling
What are some examples of hermaphroditic animals and why is this advantageous to them?
Many sessile animals (like barnacles), burrowing animals (like clams) and parasites (like tapeworms) are hermaphroditic.
This is advantageous as these organisms are not highly motile, and the parasite may be one of a few to infect its host. Therefore they have limited ability to find a mate so hermaphroditism is advantageous.
Is hermaphroditism a form of asexual reproduction?
No, the idea is that any two organism can mate i.e. one acts as a female and the other acts as the male.
In some species, however, “self-fertilisation” occurs. In this case the genetic material of one parent is used and thus it is asexual.
What is a “harem”
A group of females with a single male.
What is an example of an animal that lives in a harem?
The blue-head wrasse fish.
FYI: in Muslim societies a “harem” refers to a separate part of the house reserved for wives and female servants
What happens when the sole male of a blue-head Wrasse fish harem dies?
On of the females (often the largest) changes gender into the male.
What is an example of an organism, besides the wrass, that undergoes sex reversal? What advantage does it offer?
Young oysters release sperm but as they age and reach full size they develop into egg-releasing females.
This adaption maximises gamete production, which is important as oysters reproduce by releasing gametes into the ocean.
The small males produce large amounts of sperm as it is small. Small females would not be able to release as many eggs as these eggs are larger and thus require more energy. However by all developed oysters releasing eggs when they are large (and thus able to support such high energy use) more eggs are produced.
How can fertilisation be conceptually divided?
Internal fertilisation and “external fertilisation”
What is “internal fertilisation”?
The sperm is deposited into or near the female reproductive tract. The fusion of gamete occurs within the female.
What is external “fertilisation”?
The male and female release gametes into the environment i.e. water. These gametes fuse outside either parent.
What adaption do many externally fertilising animals employ?
They all group together and release gametes simultaneously. This is known as “spawning”
What regulates the timing of spawning?
Either chemical messages released by one of the organisms or environmental cues such as temperature, day length or moon phase.
Does external fertilisation preclude mating?
No, unlike spawning in which an entire population releases at once, some organisms perform external fertilisation during courtship.
