Reproductive Behaviour Flashcards
What are the different forms of asexual reproduction?
Fission, budding and fragmentation followed by regeneration.
Define fission in terms of asexual reproduction, give examples of species who reproduce by this method.
Binary fission, where a parent organism separates into two or more genetically identical individuals of approximately the same size. Examples include single celled prokaryotes & eukaryotes as well as some marine invertebrates including starfish and anemones.
Define budding in terms of asexual reproduction and give examples.
New individuals arise from outgrowths of the parent, then split off and live independently. Examples include yeast and hydra.
Explain fragmentation and regeneration as a form of asexual reproduction and give examples of organisms that reproduce via this method.
The body is broken into several parts and the missing parts of the newly divided bodies then regrow. Examples include annelid worms, sponges, Cnidarians, bristle worms and sea squirts.
Which organism has astonishing powers of regeneration? Outline what it is able to survive.
Sponges can be entirely macerated by passing them through a fine gauze. Cells will then regroup and grow into new individuals.
Define parthenogenesis and give examples of species which reproduce using this method.
A form of asexual reproduction where eggs aren’t fertilised. It occurs in many insects, ants, bees and wasps produce male drones by parthenogenesis. A well known vertebrate example is the whip tail lizard.
What is the primary genetic difference between male and female bees, wasps and ants (Hymenoptera)
Males (drones) are produced by asexual parthenogenesis, the eggs are not fertilised, but they become fertile adults. Females (workers and queens) are produced by sexual reproduction & have genetic recombination.
Explain the disadvantage to asexual reproduction
There is little genetic variation so asexual species are vulnerable to sudden alterations in environmental conditions.
Explain potential reproductive rate and outline how this differs between males and females and why.
Potential reproductive rate is the offspring production per unit of time each sex would achieve if unconstrained by mate availability. It is usually much higher in males than females as they make far less energetic investment in the production of gametes.
Define monogamous and polygamous and explain reasons behind which method different species choose.
Monogamous species have one male and one female which breed exclusively with each other. Polygamous breed with multiple partners. Birds are generally monogamous because their offspring require considerable care as both eggs and chicks. Survival requires both parents. Most other species are polygamous.
Why is monogamy rare in mammals?
Gestation and lactation can only be performed by the female (unlike birds) so the male is free to leave and seek further copulations.
Define polyandry, polygyny & polygynandry.
Polyandry is where one female mates with several males, polygyny s where males mate with several females & polygynandry is where both male and female mate with several other partners.
Give an example of polyandry and explain the pressure which drove the species into employing this method of reproduction.
American jacana (aka the Lily trotter) - females defend large territories in which males each defend a nest site. Females lay eggs in each nest which the male then protects and incubates. Rarity of nesting sites and risk of predation pressured this role reversal. Females are much larger than males to lay the excess quantity of eggs.
Give examples of species which exhibit ‘role reversal’ breeding strategies.
Pipefish, giant water bugs & midwife toads. In all these examples males brood young. Females are usually more competitive and evolve courtship displays.
Name three sorts of polygyny.
Female defence polygyny, resource defence polygyny & leks.
Explain female defence polygyny and give an example.
Males compete for females directly, who often congregate in large numbers in a given area due to environmental pressures. Males often compete aggressively with each other to maintain a haream. Example - elephant seals, where 10% of males fertilise almost 90% of the females.
Explain resource defence polygyny and give an example.
Males defend resources such as food or suitable nesting sites which are essential for successful reproduction. An example is the yellow rumped honey guide, a bird which feeds on bees wax. Males establish territories around bees nests.
Explain leks and give an example.
Males don’t defend either females or resources, instead they gather in large groups, called leks, on insignificant territory. The territory is simply a location for them to display courtship to visiting females. Many birds form leks, such as prairie chickens.
Define fecundity.
The number of gametes (usually eggs) produced by an individual.
Explain the difference between semelparous and iteroparous reproduction.
Semelparous indicates individuals which only breed once in their life time, and then die. Iteroparous individuals breed many times over their life time.
Outline fitness in biological terms.
The relative ability of an organism to survive and leave offspring that themselves survive and leave offspring.
Explain the theory of organisms life history.
The offset of breeding age and duration relative to lifespan. Theoretically the best life history would be to reproduce early in life, reproduce repeatedly and produce large offspring through a long life span. Such an organism doesn’t actually exist.
Explain the life history trade-off
The existence of both a fitness benefit and a fitness cost to a given history trait, relative to each other; for example devoting resources to either breeding or fitness & growth.
Explain somatic effort and reproductive effort.
Resources allocated to survival and growth are somatic effort and resources allocated to breeding are reproductive effort.
What is the likely effective on birds which raise small broods (3 or 4 chicks) compared to those which raise large broods (7 or 8 chicks) over the winter following chick rearing?
A study showed those which raised a larger brood were less likely to survive the following winter. Those who raised a small brood had substantially better odds.
Explain the difference between K-strategist and r-strategist organisms.
K-strategists maximise competitiveness and adult survival, r-strategists maximise their reproductive rate.
What are the three extant orders of amphibians?
Anura (frogs and toads), Urodela (salamanders & newts) & Gymnophina (caecilians).
