Practical 5 Flashcards
Do Salmon (species from lab 5) have internal or external fertilisation?
External Fertilisation
Are Salmon semelparous or iteroparous?
These salmon were semelparous (although Atlantic salmon are iteroparous)
What are the advantages to being semelparous?
Larger clutch size, shorter generation times, higher chance of at least one individual surviving till adulthood. Put all their resources into mating.
What are the advantages to being iteroparous?
Less individuals born but they are stronger, parental care of offspring and eggs
In female dusky flathead (Platycephalus sp.) the gonads occupy the majority of the body cavity. What does this imply about the size and number of eggs?
Large number of small eggs
Why would you expect dusky flathead to have a distinct breeding season?
lots of eggs implies that a species is more likely to have a distinct breeding season
Is sperm storage likely dusky flathead?
There is no sperm storage in females for this species as they are external fertilisers.
Do male dusky flathead have an intromittent organ?
Males do not have intromittent organs as they do not need to perform internal fertilization.
What are some unusual aspects of seahorse reproduction?
Male gives birth (females deposits eggs in males pouch)
What is the level of reproductive investment in Seahorses?
Males have a high level of investment as they must carry the eggs around in a pouch and feed the eggs with both oxygen and nutrients via a system of capillaries.
What are the advantages of males looking after the eggs in seahorses?
Males are able to protect the developing offspring as the eggs are deposited in the pouch. All the young are then deposited in a single event meaning that there is a greater chance of survival immediately prior to release.
How does the male guppy achieve internal fertilisation?
The male guppy’s anal fin develops into a gonopodium (sexual organ) to transfer sperm into the female’s cloaca
How do the life histories of the guppy and the dusky flathead differ?
Dusky flathead has external fertilisation and larger clutch sizes proportional to the fish, while guppy has larger investment and smaller clutch sizes (going for larger survival rate
However guppy is more r-selected, as they mature faster and don’t live very long, while the flathead is k-selected due to growing large and other attributes, despite having many offspring. Therefore, guppy’s are also ovoviviparous.
How do sharks achieve internal fertilisation?
The male sharks have two claspers to anchor themselves to the female, and then transfer sperm pockets into the female through the clasper into the cloaca Claspers are an evolutionary hallmark for sharks, one of the first to develop internal fertilisation.
What is oviparity?
albumen and a horny outer shell are secreted by the nudimental gland in the oviduct to form an egg case. Vitellogenesis (the process of provisioning eggs) occurs, before they are ovulated with energy-rich supplies.
What is ovo-viviparity?
the eggs develop in the oviduct, with development fuelled predominantly from the egg yolk before hatching and birth occurs. Nutrients may be added during development via histotroph secretions from the uterus
What is viviparity?
the embryo develops with the direct provision of nutrients by a maternal-fetal vascular connection, via a placenta
Discuss the egg size (& yolk content), morphology, and number of offspring in oviparous species
relatively large egg size, a lot of yolk content, large morphology in development. More effective development if the egg is left alone however susceptible to prey
Discuss the egg size (& yolk content), morphology, and number of offspring in ovo-viviparous species
egg size much smaller, much more egg content, small morphology, only released from parent once developed enough to survive on its own. Much safer as eggs are still with parents however, less offspring are produced.
Discuss the egg size (& yolk content), morphology, and number of offspring in viviparous species
Egg size medium to large, little yolk content and egg becomes placenta (edible) as a form of nutrients for the egg. Number of offspring is very little however there is a lot of development offspring before release into the environment. The parent is normally very vulnerable to prey during pregnancy. True placental viviparous have little to no yolk - nutrients provided by placenta
How can one identify that a shark is a viviparous species?
Umbilical cord means placenta = viviparous
Why does a sand tiger shark produce so many eggs when only 1-2 offspring are produced?
They produce a lot of eggs in order to feed the young that are growing inside the mother, the eggs are infertile eggs, due to the embryos eating the unfertilised eggs the mother does not need to give resources to her embryos and can keep living for herself.
Anura: Internal or External Fertilisation? Intromittent Organ? Reproductive mode? Parental care?
External Fertilisation, no intromittent organ, Ovo or viviparous, no Parental care.
Caudata: Internal or External Fertilisation? Intromittent Organ? Reproductive mode? Parental care?
Both Internal and external fertilisation, no intromittent organ, Mostly oviparous but very little are viviparous, most have no parental care but some tropical species do.
Gymnophiona: Internal or External Fertilisation? Intromittent Organ? Reproductive mode? Parental care?
Internal fertilisation, does have an intromittent organ, Oviparous and viviparous and does have parental care
How does internal fertilisation occur in salamanders?
Reproduce by having internal fertilisation without sex. Males drop sperm caps into an internal pouch called the spermatheca and the eggs are fertilised from there
How does external fertilisation occur in salamanders and newts?
A Lot like frogs, females deposit eggs in an area and then males deposit sperm on top
Do squamate reptiles use both hemipenes when mating?
No - they only use one at a time
Do squamate reptiles receive parental care after hatching/giving birth?
no
how do clutch/litter size vary between oviparous and viviparous squamate reptiles?
larger clutch size with oviparous. Smaller litter size with viviparous reptiles
Viviparity has evolved on more than 100 separate occasions in squamate reptiles. What environmental conditions do you think might favour viviparity? Why do you think viviparity has evolved so often in squamate reptiles?
Easier to avoid predators, better nutrient supply via placenta, viviparous individuals are found in cooler areas. No recorded instance in whole group - strong phylogenetic constraint. Cold environments favour viviparity in reptiles, as they require warm external environments to thermoregulate, and cold environments may be suboptimal for egg development, so live birth allows the young to thermoregulate from a younger age.
What is unusual about the eggs of pig-nosed turtles?
Requires eggs being submerged in water in order for the baby turtle to hatch. Hatching of the eggs to coincide with the rainy season in order to maximise best conditions.
What are some potential benefits of post-hatching parental care in crocodilians
Less likely to be predated, can provide food for young
What are the potential benefits of viviparity in the life history of sea snakes
If it laid eggs it would need to lay eggs outside of water (due to being an amniotic egg it will sink and drown in water), viviparity allows the snakes to have young in the water without having to go to land.
How do birds achieve internal fertilisation without an intromittent organ?
Lining up cloacas. “Kissing”
Only the left ovary is usually functional in birds. How might this influence the timing and production of eggs? How does this impact the life history strategies of birds?
It means they only produce one egg at a time.
This can cause eggs in a nest to be older than others, as they were laid earlier. Birds get around this sometimes by laying eggs but not incubating them until they are all laid (or at least most of them)
Kiwis are the only bird with two ovaries.
What are some potential explanations for why there are no viviparous bird species?
Harder to fly with a heavy embryo.
How many chicks do penguins usually have? List some general life history characteristics of penguins.
Usually 2 chicks. Penguins are Iteroparous. Altricial young (can’t do much). Just need to be fed while they grow.
Describe the eggs produced by monotremes (e.g. size, yolk content). Is milk provided to the young? Discuss the life history strategy (e.g. clutch size, maternal investment) of monotremes
Relatively small eggs with high yolk content. Small clutch size (1 or very few eggs) with high maternal investment. Short gestation. Milk provided (no nipples)
Outline the main features of the marsupial life cycle. What aspects of the Australian environment might favour the marsupial reproductive strategy?
Mating: internal fertilisation. After birth, young climb into mother’s belly/pouch for nursing (grabbing a nipple and feeding off a constant supply of milk). Marsupials have small litters (normally between 1-3 offspring). After weaning, offspring roam and find their own food however stay with their parents quite a bit (normally for protection or rest). After many months, they go off on their own.
Due to the arid environment of Australia, marsupials survived due to having mobility of being able to carry their young in pouches as opposed to mammals having to invest many resources into gestation. If environments proved too harsh, the marsupials could ditch their young for their own survival.
How would you describe the reproductive strategy evident in Antechinus (small rat like animal)? What are some advantages and disadvantages of this reproductive and life history strategy?
They are Semelparous. A potential disadvantage is scrambled competition due to relying on insect boom for feeding, have young as insects boom
how do bacula variation in mammals relate to their mating and reproductive behaviours
A larger, stronger baculum may be easier to maintain a long period of intermission.
What are some advantages and disadvantages of giving birth at sea?
Advantage: Don’t need to develop the ability to get onto and off land. Morphology can be more specialised for aquatic locomotion.
Disadvantage: the speed required and potential exposure to predators.
Why do some marine mammals haul out onto land to give birth?
Offspring need to be able to breathe.
Outline and discuss the life cycle and life history strategies of marine mammals
Generally K-selected species
