Reproductive Animal Strategies

Question 1

define reproduction

Answer 1

the production of a new generation of organisms from an existing generation, it ensures the continued survival of a species

Question 2

what is the goal of each species and what is it known as

Answer 2

to produce the maximum number of surviving offspring while using the least amount of energy (this is called reproductive effort)

Question 3

what is the difference between asexual and sexual reproduction

Answer 3

asexual - found in lower and microscopic animals, is energy efficient because it only involves one animal

sexual - happens in all vertebrates, is much more complex which needs higher energy input

Question 4

what have unique reproductive strategies allowed

Answer 4

maximum reproductive success in different environments enabling the species to breed successfully and then survive to reproductive age

Question 5

name 6 reproductive strategies

Answer 5

1. Courtship
2. External versus internal fertilisation
3. Ovipary, ovovivipary and vivipary
4. Amniotic egg
5. Precocial and altricial development
6. Parental care

Question 6

what is courtship

Answer 6

behaviour and/or signals that are designed to attract another animal for mating and breeding

Question 7

what are examples of simple courtship strategies

Answer 7

chemicals (pheromones), visual (brightly coloured body parts), auditory (mating calls)

1. moths produce specific pheromones that guide males towards them
2. most frogs have to return to the water for mating and breeding, once the males reach the mating ground they sing (grunt, croak) to attract females, each species have a specific song that only attracts females of that species

Question 8

what are examples of complex courtship strategies

Answer 8

more elaborate forms of courtship, females are usually attracted to larger males, who have more elaborate physical features and who display more energy during the courtship activity (these characteristics reinforce pair bonding and promise healthier offspring that are more likely to survive)

1. The blue cranes courtship display includes a complex and extended series of calls as well as an elaborate dance done by the males
2. Springbok have an annual rut (period of sexual excitement) during which the males defend their territories with loud grunts, attack vegetation with their horns and deposit middens of urine and dung in a ritualised display in order to attract females (most young are born 6 months later in spring just before rainy season) so the timing of this ritual also ensures that mothers are in good condition and that there will be enough food for the newborns
3. Male Hoopoes feed insects to their mates, allowing the females to save their energy for incubating and breeding

Question 9

how does courtship maximise reproduction

Answer 9

• it ensure that males and females are suitable mates
• sexual behavior is timed so that males and females are ready for mating at the same time
• energy expenditure is usually by the male so that the female conserves her energy for breeding

Question 10

define fertilisation

Answer 10

the joining of the nucleus of an egg and a sperm. the sperm are motile as they’re able to swim but eggs don’t move, therefore vertebrates have ways of ensuring that sperm reach the eggs for fertilisation to take place

Question 11

explain external fertilisation

Answer 11

it takes place in water and occurs in most aquatic vertebrates (fish and frogs)

Question 12

why is external fertilisation not ideal

Answer 12

• it is wasteful as huge numbers of eggs are produced, most of the eggs are eaten
• fertilisation is not certain

Question 13

how can external fertilisation maximise reproduction

Answer 13

• huge numbers of of eggs and sperm are released into the water to increase the probability of fertilisation. with the large number of fertilised eggs there are enough to grow into adulthood even though many are lost to predation
• eg. many fish swim side by side when releasing their eggs and sperm which ensure the gametes are close together

(energy expenditure goes almost totally into producing the large number of eggs)

Question 14

explain internal fertilisation

Answer 14

occurs in terrestrial vertebrates (reptiles, birds and mammals) the sperm is released directly into the body of the female and fertilise the eggs inside the body

Question 15

examples of internal fertilisation

Answer 15

• most birds and reptiles mate using a cloaca (a single opening in the lower abdomen) during mating the males and females line up their cloaca for the transfer of sperm
• the males of virtually all mammals have a penis to introduce the sperm into the female, this process is known as copulation (the penis ensures that the sperm is transferred successfully without being destroyed by any environmental conditions)

Question 16

how does internal fertilisation maximise reproduction

Answer 16

fertilisation is more certain as the gametes are plcaed as close together as possible, although it doesn’t ensure fertilisation it makes it much more likely. fewer gametes are therefore needed, so energy saved in production of gametes can be used for other purposes to maximise reproduction, eg. a protective shell and increased yolk can be produced or development can be internal via a placenta

Question 17

what do ovipary, ovovivipary and vivipary strategies describe and indicate

Answer 17

the terms are used to describe the moment at which the future offspring separates from the parent

and they indicate where the embryo develops and how the embryo and fetus are nourished

Question 18

what is ovipary

Answer 18

where the eggs develop outside of the parent, they may be fertilised internally or externally, the majority of animals are oviparous, egg yolk is the only food that the developing embryos receive until they have hatched

Question 19

how does ovipary maximise reproduction in aquatic environments

Answer 19

most fish and amphibians are oviparous, the eggs are released into the water and they’re fertilised externally, lots and lots of eggs are needed as the developing eggs are very vulnerable to predation. the famales have to use high amounts of energy to produce the eggs however they save energy by not needing yolk production and parental care.

Question 20

give examples of oviparous animals

Answer 20

• catshark females lay eggs that are known as mermaids purses, these egg cases contain the embryo and yolk supply and the young shark eventually hatches out of the case. the egg case negates the need for large numbers of eggs as the developing animal is well protected

Question 21

how does ovipary maximise reproduction in land environments

Answer 21

these include most reptiles (70%) and birds

1. very few eggs are produced particularly by birds therefore saved energy goes into:
   - producing eggs with more food (nutrient rich yolk and protein rich albumen) which allows the animal to be more formed at hatching
   - protecting and incubating the eggs before hatching
   - parental care for the young
2. a shell protects the developing embryo from predators, pathogens, physical damage and dehydration

Question 22

what is ovovivipary

Answer 22

animals where the eggs that are fertilised internally are kept inside the females body until they hatch, therefore the offspring are born live

Question 23

how is the developing embryo nourished

Answer 23

the embryo gets food from the large amount of yolk in the egg and is not dependant on the mother except for physical protection and often gaseous exchange

Question 24

give an example of an ovoviviparous animal

Answer 24

the ragged tooth shark, whose eggs are fertilised internally, the embryos initially feed on their own supplies of yolk, later they feed on fertilised eggs and other developing embryos (inter-uterine cannibalism) this results in only two pups being born per litter
gestation is 9-12 months depending on water temperature

Question 25

how does ovovivipary maximise reproduction

Answer 25

it occurs in some fish and reptiles (puff adder)
maximises reproduction because:

• fewer eggs are produced so mothers energy expenditure is less
• the developing embryo is much less vulnerable to predation and cold temperatures
• the young are born fully developed so they’re able to get their own food and escape predators more easily

Question 26

what is vivipary

Answer 26

animals where fertilisation is internal and the eggs don’t have a shell, the retained egg forms an embryo and then a fetus, which develops inside the mother.

Question 27

where do these embryos get nourishment

Answer 27

they obtain continuous nourishment from their mother, usually through a placenta and is then born live

Question 28

where does vivipary occur

Answer 28

• placental animals

- about 55% of sharks and rays

Question 29

how does vivipary maximise reproduction

Answer 29

the reduced number of eggs means that more energy is available yo:

• nourish and protect the developing embryo and fetus
• provide parental care after the young are born

this results in a higher chance of the offspring surviving and reaching reproductive age

Question 30

give an example of vivipary

Answer 30

the hammerhead shark, the mother joins with its developing embryo via the yolk sac that forms a connection with the mothers oviduct tissue, it is through this that the developing young receive nourishment until they’re ready for birth, the young are born live and fully functional

Question 31

explain the difference between early vertebrates and later vertebrates

Answer 31

early vertebrates (fish and amphibians) need to lay their eggs in water and therefore can’t live far from water, they have simple eggs with no shell

later vertebrates (reptiles and birds) known as amniotes can lay their eggs in terrestrial environments as they no longer have to return to water for breeding, mammals are also amniotes but don’t lay eggs (the eggs are retained in their bodies)

Question 32

what do all amniotes produce

Answer 32

eggs that, after fertilisation, develop extra-embryonic membranes. These are fluid filled membranes (amnion, allantois, yolk sac, chorion) that allow the embryo to survive and develop on land - or in the case of mammals, internally in the uterus. fertilisation is internal and the membranes develop after fertilisation

these eggs are called amniotic eggs

Question 33

why are amniotic eggs a major evolutionary innovation

Answer 33

they allowed some of the first reptiles to colonize dry land more than 300 million years ago

Question 34

draw a diagram of a typcial amniotic egg

Answer 34

page 79

Question 35

how does an amniotic egg maximise reproduction

Answer 35

the amniotic egg maximises the development of the embryo and fetus before hatching/birth enabling the offspring to survive the harsh conditions on land more easily and successfully

• the fluid filled amnion surrounds and protects the embryo against dehydration and mechanical injury
• the allantois acts as a reservoir for nitrogenous waste in birds and reptiles (in aquatic environments waste would pass directly into water)
• the yolk sac in birds and reptiles holds nutritious food for the embryos development
• the chorion surrounds all the other membranes where in birds and reptiles allows for gaseous exchange together with the shell, and in mammals it forms the placenta with the endometrium

Question 36

what has precocial and altricial development evolved to

Answer 36

• provide nourishment to the developing embryo and young

- protect them from predation

Question 37

what are precocial species

Answer 37

species that hatch or are born when they are almost fully developed. therefore parental energy expenditure goes into pre-natal developments (the mothers are less involved after birth)

Question 38

what are some characteristics of precocial species at hatching/birth

Answer 38

• open eyes and hair/down
• have large brains relative to their body size
• are immediately active and mobile (even though they may not be very steady)
• usually not confined to nests (birds have well developed feet and legs)

Question 39

how does precocial development maximise reproduction

Answer 39

the precocial features help offspring to:

• find and eat food on their own
• look after themselves against predators

therefore the offspring have better chances at survival

Question 40

what are examples of precocial species

Answer 40

• ground nesting species (penguins, chickens, ducks and ostriches)
• large mammals (elephants, hares, wildebees)

Question 41

what are altricial species

Answer 41

species that are born/hatch when they are not well developed, so parental care energy expenditure goes into post-natal development of the offspring

Question 42

what are some characteristics of altricial species at hatching/birth

Answer 42

• often naked, lacking hair/down
• cannot walk or fly
• often have eyes closed
• rely entirely on their parents for warmth, transport and food
• have a coloured mouth-lining or gape-edge (birds)
• require care and protection for a comparatively long time

Question 43

how does altricial development maximise reproduction

Answer 43

it allows more offspring to reach reproductive maturity because:
- there is parental care, the parents save energy on pre-natal care and therefore have more energy to feed, brood, and protect their young post-natal

• the offspring reach reproductive age quickly because they are easier to feed as they stay in their nests, and grow very rapidly as they are fed large nutrient rich food items
• they are also safer from predation as the nests are inaccessible and the offspring only leave the nest once they’re fully grown and ready to evade predation alobe

Question 44

what are examples of altricial species

Answer 44

• small mammals (rodents, cats, dogs)
• humans
• tree nesting birds
• marsupials (young are cared for in a pouch)

Question 45

what is parental care

Answer 45

any type of behaviour in which a parent spends time or energy to improve the survival, condition and future reproductive success of the offspring

Question 46

draw a diagram to show the result of parental care on a number of eggs…

Answer 46

page 82

Question 47

give examples of what pre-natal, and post-natal care consists of

Answer 47

pre-natal care - guarding eggs, building nests, carrying broods, incubating eggs, placental nourishment

post-natal care - providing food, protection, teaching offspring

Question 48

what does parental care in fish consist of

Answer 48

most fish species show no parental care, no fish feed their young. in about 20% of fish species there is little parental care.

this care involves:

• building nests,
• guarding eggs and hatchlings from predators,
• fanning eggs to increase oxygen supply,
• cleaning eggs to eliminate fungus
• having a brood pouch (seahorses)

Question 49

what does parental care in amphibians consist of

Answer 49

most amphibians return to the water for reproduction,

much of their parental care is directed to minimalise the loss from predators of eggs and embryos by:

• egg guarding (eggs of the midwife toad are kept and carried on the rear end of the male)
• building terrestrial-breeding sites away from water (foam nest frog female secretes a fluid that us churned up with her hind legs into a foam ball to form a nest in trees that hang over water, the fertilised eggs are protected and stay moist inside the ball, once the tadpoles hatch they drop into the water below)

Question 50

what does parental care in reptiles consist of

Answer 50

they show virtually no parental care besides guarding eggs (lizards and snakes), incubation by body heat (pythons), attacking predators (pythons)

Question 51

what does parental care in birds consist of

Answer 51

they show extensive parental care (both parents)

including;

• incubation of eggs by using body heat
• nest building (protects eggs from predators, sun, rain)
• brooding (as the offspring can’t thermoregulate) and feeding
• protecting against predators
• teaching young how to get food

Question 52

what does parental care in mammals consist of

Answer 52

most young mammals are completely helpless at birth, so they require intense parental care

maternal care includes:

• lactation, the composition of each species milk is perfect for the best possible development of that species
• protection against predators and the cold
• teaching to gather food
• licking newborn immediately after birth to establish a unique relationship (no licking will result in the newborn rejecting the mother)

paternal care includes:

• feeding the young
• guarding against predators

some mammals (rodents and carnivores) make special nests (burrows)

Question 53

what is an example of k-strategy species

Answer 53

Elephants - 70 year life expectancy, begin mating at about 20 years old

• only a few offspring are produced , female elephants have babies about 3 years apart and only have 1 at a time
• high level of parental care so the young have a high chance of surviving, the whole group looks after and protects the young, through childhood and adolescence
• elephants are a climax species as they produce only slightly more offspring than the maximum that the environment can hold (population density)

Question 54

what is an example of r-strategy species

Answer 54

leatherback and loggerhead turtles - live between 50 and 100 years, become sexually mature late (about 17 years old) this allows the females to put more energy into producing eggs as she doesn’t need energy to grow

• they lay numerous eggs (multiple clutches of 90 and 130 eggs each) every 2-3 years
• no parental care, so only a few offspring will survive (between 2-10 per 1000 eggs laid will reach adulthood)
• low survivorship is due to predation while they are still inside the eggs and when they go into the sea (predation will only decrease when body size increases)

Question 55

what are survivorship curves

Answer 55

the pattern of mortality of each species expressed as a curve

Question 56

what do different curves mean on a survivorship curve, give examples of what species would create that curve and why

Answer 56

convex curve:

• most of the offspring become adults
• death occurs mainly amongst older individuals
  eg. k -strategy species, elephants, humans
  because: these species have high levels of parental care and therefore high survival rate

straight line:

• mortality decreases slowly with time
• a young organism is just as likely to die as an old one
  eg. birds and plants

concave curve:

• few offspring become adults
• high mortality rate when they’re young
• once they’re established there is an improvement in life expectancy
  eg. r strategy species, turtle
  because: these species have no parental care and therefore have a low survival rate when they’re young