Lecture 7-Reptiles 4 (Reproduction)

Question 1

What does it mean that reptiles are ectotherms?

Answer 1

-use their behaviour to maintain heat -have a more efficient Krebs cycle (fewer protons are lost) -being ectothermic provides reptiles with lot of flexibility on where they can live and what they can do, (life histories)

Question 2

What is the behaviour of a reptile during the day like in terms of maintaining core temperature?

Answer 2

-temperature is quite stable throughout the day -regulate behaviourally, have to move between shade and sun depending on the temperatures -when high= go into shade, low=go into sunny areas -use external energy and environment to regulate body temperature

Question 3

Do ectotherms have lower energy needs than endotherms?

Answer 3

-yes -more efficient body system, don’t need to generate as much heat -cost of life is lower -metabolic rate decreases with mass -low energy, variable temperature systems

Question 4

How are reptiles as ectotherms limited in where they can live in the world?

Answer 4

-can’t go too close to the poles= about 40S and 40N as they need sun

Question 5

What is a life history?

Answer 5

-An animal’s pattern of allocation, throughout life, of time and energy to various key activities, such as growth, repair of cell and tissue damage, and reproduction. -growth, maintenance, reproduction

Question 6

What is maintenance?

Answer 6

-keeping the systems at some level -maintaining homeostasis

Question 7

What are the K and R selected species? example: lizard and turtle

Answer 7

K- turtle= long life slow growing , takes 30 yrs to grow up, then some maintainance, then some ebergy to reproduction R- lizard= only takes 9 months to grow, puts more resources into reproduction than anything else

Question 8

What is the life history of a green Sea turtle?

Answer 8

-turtles born, go into the ocean, then dispersing and finding habitat -grow in pelagic habitat= in the currents, spend that just floating in a raft and eating, growing (good for them, not as much predation) -when big enough move to feeding habitat, then spend 30 years there to grow, then mature sexually -females huge input= 120 eggs every 5 to 6 years -males don’t have to pay costs as much (no migration or egg production) so the males can reproduce more times -more reproductive opportunities= males -overall restricted in reproduction opportunity so they try really hard to succeed

Question 9

What are the three factors influencing life histories of reptiles?

Answer 9

1. Environment (temperature) 2. Ecology (diet) 3. Phylogeny (limits of design= can’t fly if doesn’t have wings etc.)

Question 10

What does reproduction comprise?

Answer 10

-physiology, morphology, behaviour -these can act together to produce different life-history traits (different schedules) -reproduction is the big ticket item in the life history of all animals!

Question 11

What is the variation in reptile life histories: Age to reproductive maturity?

Answer 11

Age to reproductive maturity: 9 month to 45 years (lizard/turtle)

Question 12

What is the variation in reptile life histories: Active output per breeding event?

Answer 12

2 vs 600 offspring (geckos 2- turtles= 600 in a season)

Question 13

What is the variation in reptile life histories: number of breeding events?

Answer 13

1-20+

Question 14

Can environment change the strategies of breeding of different populations of the same species?

Answer 14

-even different populations of the same species that live in slightly different environments change their strategies depending on the environment etc.

Question 15

What three factors of reproduction does temperature affect in reptiles?

Answer 15

1.Timing/patterns of annual reproduction 2. Modes of Incubation 3. Sex determination

Question 16

What are the 5 stages of a reptilian reproductive cycle and their comparative duration?

Answer 16

1. Physiological activation of reproductive system: make sperm and maturate eggs
2. Courtship and mating
3. Ovulation and fertilization (1+ times)
4. Egg laying and incubation/or embryo development in utero (1+ times)
5. Hatching or birth

Question 17

How do the reproductive cycles differ in a lizard living in warmer and colder climate?

Answer 17

• depends on where you are, if in the north= try to time it so the offspring come out in early summer
• southern part= activate in autumn, then go to sleep, then in spring= courtship, hatching is in late summer

picture:

1. Physiological activation of reproductive system: make sperm and maturate eggs
2. Courtship and mating
3. Ovulation and fertilization (1+ times)
4. Egg laying and incubation/or embryo development in utero (1+ times)
5. Hatching or birth

Question 18

Does temperature have effect on reptilian development in eggs and in utero?

Answer 18

yes, crucial!

Question 19

What effects does temperature have on development of eggs?

Answer 19

-the rate at which eggs develop is dependent on the environment -that is why the dig to bury them but small reptiles can’t dig very deep

Question 20

What are oviparous reptiles?

Answer 20

-Reptiles that lay eggs

Question 21

What is oviposition?

Answer 21

-The act of laying eggs

Question 22

What do viviparous reptiles do?

Answer 22

-bear live young -extended retention of eggs -loss of shell nutrient transfer -placenta

Question 23

How many times has viviparity evolved in reptiles and in mammals?

Answer 23

-100 times in reptiles -1 time in mammals

Question 24

What causes viviparity in reptiles?

Answer 24

-environment -cold temperatures -that way the mother can control the temperature of the eggs, otherwise they would die in the cold -Allows female lizards to control developmental temperature of offspring.

Question 25

Can the effect of temperatures during development be seen after birth/ hatching?

Answer 25

-Developmental temperatures have a major affect on the fitness of reptiles by influencing phenotypes of offspring -if you incubate at different temps= get different phenotypes -developmental tem has a huge influence on the performance of the hatchlings -permanent developmental effect -hot nests= fast runners, cold nests= slow runners

Question 26

How can sex be determined in reptiles?

Answer 26

1. ZZ (male)/ ZW (female) or XX / XY Chromosones. 2. non-genetic temperature sex determination (TSD or ESD)

Question 27

What reptiles have temperature dependent determined sex?

Answer 27

-some turtles -some lizards -all crocodiles -no snakes! (as far as we know)

Question 28

What are the three patterns of TSD involving temperature of incubation of the eggs?

Answer 28

1. as temp increase = more females for lizards
2. opposite for turtles, higher temp=males
3. females produced at both extremes

Question 29

Why did some reptiles evolve TSD?

Answer 29

-Selection should favour TSD over genotypic sex determination when the developmental environment differentially influences male versus female fitness. That means that under certain incubation temperatures one sex performs better than the other!!

Question 30

How do reptiles maximize offspring fitness in reproduction?

Answer 30

-Because temperature influences offspring phenotypes, reptiles have evolved ways to maximize offspring fitness through viviparity and temperature sex determination.