Flashcards in Reproductive Behaviour Deck (69):
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.
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).
Outline the diversity of anurans.
First appeared 200 million years ago and now contain 54 families and over 6000 species. Found everywhere from deserts to alpine forests, they inhabit all continents except Antarctica.
What is the world's smallest known vertebrate?
A tiny frog from papa New Guinea measuring just 7.7mm
Explain the main two types of breeding in frogs and toads.
Explosive breeders - breeding over a short time period of few days to a few weeks and prolonged breeders who breed over periods of six months or more.
Why would frogs that live in deserts breed explosively?
Any pools available are the short term consequences of heavy rainfall which they must make use of while they can.
Outline the process of external fertilisation in frogs
Males clasp females under the armpits in a hold called amplexus. She then moves to suitable water and releases her eggs in a process called oviposition. The male then secretes his sperm into them and fertilisation occurs.
Explain scramble competition in frogs
A horrible ball of rape resulting from males grasping anything that moves in an attempt at securing the amplexus grasp. Females sometimes drown as a result of being under the grasp of multiple males who are trying to breed with her.
Outline the process of prolonged breeding in frogs
Occurs over a six month period, usually coinciding with tropical rains. Males chorus to attract females and rarely initiate amplexus. Instead females approach their chosen mate and touch them to signify an invitation to amplexus so mating can occur. It's generally more civilised.
What is one of the most important functions of courtship signalling? Give an example of how this can be used.
Confirming species identity. Breeding with a different species is highly maladaptive because the offspring which result either die or are infertile. An example is the different patterns of signalling seen in different species of firefly.
Outline the roles communication plays within the context of reproduction.
Besides identifying species, mating calls also allow females to select a mate based on the indication of the strongest male/loudest roar. It also allows males to combat vocally, minimising physical violence.
What two types of selection pressure are likely to act on animal signals in the context of reproduction?
Selection for conspecific mate recognition and selection for mate quality.
What properties of mating calls are likely to be static (stereotyped) and which are likely to be more dynamic (show high variability within species)
Properties that are involved in mate recognition are likely to be static (more stereotyped) whereas those that are involved with mate quality are likely to be dynamic (more variable).
What is an oscillogram? How is it used to study mating behaviour?
The trace produced by an oscillograph or oscilloscope that, for sounds, depicts how the amplitude of the sound changes with time. Amplitude is related to the intensity of a sound which in turn is related to its loudness. Used to measure frog mating calls.
Outline the four basic parameters used to analyse frog calls.
the intensity (loudness) of the call, its frequency (pitch), the duration of the call, its repetition rate (the number of times it repeats over a given time period).
What are phonotaxis experiments?
Phonotaxis is defined as the ability to move in an oreientation with respect to a source of sound. Phonotaxis experiments are used on a wide variety of animals to better understand vocal communication systems.
What are the amphibian papilla & basilar papilla?
Two organs within the amphibian inner ear. Amphibian papilla is sensitive to low frequency sounds & basilar papilla is sensitive to high frequency sounds.a
Define intrasexual selection.
Selection that influences the evolution of characters which affect the outcome of competition among members of one sex for access to members of the opposite sex. For example deers antlers.
How does sexual selection promote traits that would seem to decrease fitness?
Sexual selection selects for extreme phenotypes in one sex, and those extreme variations often place the individual at a disadvantage for survival (e.g. a peacock’s longer tail will make him more visible to predators and slower in escaping). However, since these traits increase fitness by increasing mating success, sexual selection remains an active force in the population.
Define intersexual selection.
Evolution of secondary sexual characteristics designed to woo a mate rather than fight members of the same sex for breeding rights. For example, a peacock's tail.
Define sexual selection including its main two components.
Special case of natural selection that define an individual's ability to mate successfully. Intersexual selection are characteristics which attract a mate (woo) and intrasexual selection are characterises to compete with your own gender (fight).
What potential costs are there to a female choosing a mate rather than breeding with the first conspecific male they encounter?
Increased risk of predation by movement near ambush predators while mate seeking. Increased energy expenditure by moving some distance seeking a mate & increase time costs from mate searching, delaying successful breeding opportunity.
What are the direct benefits to females choosing a mate rather than breeding with the first conspecific male?
Direct benefits of female choice are those that enhance a female's immediate reproductive output, e.g. territory quality, parental care.
Why might female frogs select mates that are close to them in size?
Females that chose males that are closer to them in size (i.e. large males) benefit from having more eggs fertilised, because when the size difference between males and females is small the female’s cloaca is closer to the male’s.
What are the indirect benefits to female mate selection?
Indirect benefits of female choice are those that confer genetic benefits to a female's offspring through increased offspring survival & attractiveness to future partners. These choices aren't made on the basis of food supplies or nesting grounds.
What is the 'good genes' hypothesis?
Under the ‘good genes’ scenario, phenotypic differences among males provide females with information about a male’s genetic quality. Males that display certain characters (such as bright feathers or fast call rate) are of high overall genetic quality & indicates genetic factors such as resistance to parasites.
Define 'arbitrary preference' in female mate selection.
Mating choices which reflect neither greater access to resources nor genetic integrity but are instead based on an arbitrary preference, such as a given mating call proving a greater degree of auditory stimulation.
Define phylogenic constraints
Constraints arising from the phylogenic history. For example, birds devolving wings and flight muscles limited the number of eggs they could lay in one clutch. They give birth to one egg at a time, unlike reptiles who lay dozens at once.
What is phylogenic reconstruction?
A method employed by evolutionary biologists to try to provide plausible evolutionary histories for female mate choice and male traits where fossil evidence doesn't exist. This helps distinguish current adaptation from historical traits.
Define 'biological species concept'
A definition of species as a group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. It they can mate successfully, giving rise to fertile offspring, they are the same species.
Define the process of speciation.
Speciation (the formation of new species) therefore involves the evolution of reproductive barriers to the production of viable offspring so that the exchange of genes between individuals in a previously interbreeding population no longer occurs.
Outline the prezygotic (pre mating) mechanisms of speciation.
Ecological (they occupy different habitats so rarely meet), seasonal (different flowering or mating times, or age of sexual maturity), ethnological (differing courtship displays), mechanical (physical alterations to genital structure) and gametic (gametes fail to unite).
What are the postzygotic (post mating) mechanisms of speciation, give examples.
Hybrid inviability (fertilisation occurs but doesn't develop, for example cross between sheep and goats). Hybrid sterility (zygotes develop but offspring are infertile, for example crossing horses and donkeys). Hybrid breakdown (fertile offspring are produced but the fertility of offspring is reduced, occurs more often in plants)
Define allopatric speciation.
Occurs when what was once a continuous population is divided into two by some kind of physical barrier. After a period of time the two populations diverge from one another genetically to the point at which mating between individuals from the two populations does not occur successfully.
Define sympatric speciation.
Occurs in populations that are not geographically separated from one another. Nonetheless, gene flow between them is reduced if, for example, individuals occupy different ecological niches Most common examples are those that involve ecological isolation or seasonal isolation. Polyploidy is another example of sympatric speciation.
The multiplication of whole sets of chromosomes usually as a result of failure of cell division during mitosis or meiosis.
Define parapatric speciation.
Parapatric speciation occurs in continuous populations but individuals are more likely to mate with geographic neighbours than with individuals that occupy more distant parts of the geographic range. This results in a decrease in gene flow across the population range and the eventual formation of separate species.
Define sensory exploitation with regard to reproductive behaviour.
The adaptive evolution of traits in the competitive sex that evolve to exploit pre-existing sensory biases in the choosy sex. The bias in the choosy sex is pre-existing and evolved in a non-mating context.
Outline an example of speciation by polyploidy
Grey tree frogs. Eastern grey tree frog are tetraploid (4 sets of chromosomes) & cope's tree frog is diploid (2 sets of chromosomes). It is visually impossible to tell them apart. Crossing the two results in triploid offspring who die as larvae or are infertile.
Explain the trade off between the amount of time anurans spend as tadpoles and their size at metamorphosis.
Large froglets (large metamorphism) must spend longer as tadpoles to achieve this size, which leaves them vulnerable to predation for longer. Smaller froglets can progress to adult form sooner but are disadvantaged with lessened reproductive potential.
What is the key to life stage metamorphosis? What triggers them?
Hormones within the endocrine system.
What is prolactin and what role does it play in the anuran life cycle?
A stress hormone produced by the pituitary gland. During the pre-metamorphosis stage of development it stimulates growth but inhibits metamorphosis.
What hormone drives anuran metamorphosis? Explain how it is produced and used throughout the life cycle.
Thyroid stimulating hormone (TSH) which triggers the release of thyroxin. Secreted in very small quantities in the pre-metamorphosis stage. During pro-metamorphosis TSH levels rise when stimulated by CRH (corticotropin releasing hormone) until hind limb development begins.