Practical 5

Question 1

Do Salmon (species from lab 5) have internal or external fertilisation?

Answer 1

External Fertilisation

Question 2

Are Salmon semelparous or iteroparous?

Answer 2

These salmon were semelparous (although Atlantic salmon are iteroparous)

Question 3

What are the advantages to being semelparous?

Answer 3

Larger clutch size, shorter generation times, higher chance of at least one individual surviving till adulthood. Put all their resources into mating.

Question 4

What are the advantages to being iteroparous?

Answer 4

Less individuals born but they are stronger, parental care of offspring and eggs

Question 5

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?

Answer 5

Large number of small eggs

Question 6

Why would you expect dusky flathead to have a distinct breeding season?

Answer 6

lots of eggs implies that a species is more likely to have a distinct breeding season

Question 7

Is sperm storage likely dusky flathead?

Answer 7

There is no sperm storage in females for this species as they are external fertilisers.

Question 8

Do male dusky flathead have an intromittent organ?

Answer 8

Males do not have intromittent organs as they do not need to perform internal fertilization.

Question 9

What are some unusual aspects of seahorse reproduction?

Answer 9

Male gives birth (females deposits eggs in males pouch)

Question 10

What is the level of reproductive investment in Seahorses?

Answer 10

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.

Question 11

What are the advantages of males looking after the eggs in seahorses?

Answer 11

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.

Question 12

How does the male guppy achieve internal fertilisation?

Answer 12

The male guppy’s anal fin develops into a gonopodium (sexual organ) to transfer sperm into the female’s cloaca

Question 13

How do the life histories of the guppy and the dusky flathead differ?

Answer 13

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.

Question 14

How do sharks achieve internal fertilisation?

Answer 14

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.

Question 15

What is oviparity?

Answer 15

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.

Question 16

What is ovo-viviparity?

Answer 16

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

Question 17

What is viviparity?

Answer 17

the embryo develops with the direct provision of nutrients by a maternal-fetal vascular connection, via a placenta

Question 18

Discuss the egg size (& yolk content), morphology, and number of offspring in oviparous species

Answer 18

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

Question 19

Discuss the egg size (& yolk content), morphology, and number of offspring in ovo-viviparous species

Answer 19

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.

Question 20

Discuss the egg size (& yolk content), morphology, and number of offspring in viviparous species

Answer 20

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

Question 21

How can one identify that a shark is a viviparous species?

Answer 21

Umbilical cord means placenta = viviparous

Question 22

Why does a sand tiger shark produce so many eggs when only 1-2 offspring are produced?

Answer 22

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.

Question 23

Anura:
Internal or External Fertilisation?
Intromittent Organ?
Reproductive mode?
Parental care?

Answer 23

External Fertilisation, no intromittent organ, Ovo or viviparous, no Parental care.

Question 24

Caudata:
Internal or External Fertilisation?
Intromittent Organ?
Reproductive mode?
Parental care?

Answer 24

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.

Question 25

Gymnophiona:
Internal or External Fertilisation?
Intromittent Organ?
Reproductive mode?
Parental care?

Answer 25

Internal fertilisation, does have an intromittent organ, Oviparous and viviparous and does have parental care

Question 26

How does internal fertilisation occur in salamanders?

Answer 26

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

Question 27

How does external fertilisation occur in salamanders and newts?

Answer 27

A Lot like frogs, females deposit eggs in an area and then males deposit sperm on top

Question 28

Do squamate reptiles use both hemipenes when mating?

Answer 28

No - they only use one at a time

Question 29

Do squamate reptiles receive parental care after hatching/giving birth?

Answer 29

no

Question 30

how do clutch/litter size vary between oviparous and viviparous squamate reptiles?

Answer 30

larger clutch size with oviparous. Smaller litter size with viviparous reptiles

Question 31

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?

Answer 31

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.

Question 32

What is unusual about the eggs of pig-nosed turtles?

Answer 32

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.

Question 33

What are some potential benefits of post-hatching parental care in crocodilians

Answer 33

Less likely to be predated, can provide food for young

Question 34

What are the potential benefits of viviparity in the life history of sea snakes

Answer 34

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.

Question 35

How do birds achieve internal fertilisation without an intromittent organ?

Answer 35

Lining up cloacas. “Kissing”

Question 36

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?

Answer 36

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.

Question 37

What are some potential explanations for why there are no viviparous bird species?

Answer 37

Harder to fly with a heavy embryo.

Question 38

How many chicks do penguins usually have? List some general life history characteristics of penguins.

Answer 38

Usually 2 chicks. Penguins are Iteroparous. Altricial young (can’t do much). Just need to be fed while they grow.

Question 39

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

Answer 39

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)

Question 40

Outline the main features of the marsupial life cycle. What aspects of the Australian environment might favour the marsupial reproductive strategy?

Answer 40

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.

Question 41

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?

Answer 41

They are Semelparous. A potential disadvantage is scrambled competition due to relying on insect boom for feeding, have young as insects boom

Question 42

how do bacula variation in mammals relate to their mating and reproductive behaviours

Answer 42

A larger, stronger baculum may be easier to maintain a long period of intermission.

Question 43

What are some advantages and disadvantages of giving birth at sea?

Answer 43

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.

Question 44

Why do some marine mammals haul out onto land to give birth?

Answer 44

Offspring need to be able to breathe.

Question 45

Outline and discuss the life cycle and life history strategies of marine mammals

Answer 45

Generally K-selected species