1. Sex & behaviour: sexual investment CfE Advanced Higher Biology Unit 2: Organisms and Evolution

2. SQA mandatory key areas Comparison of investment in sperm and egg production – number and energy store; greater investment by females. Problems and solutions of sex for sessile organisms. Parental investment, optimal reproduction and reproductive strategies in terms of the number and quality of current offspring versus potential future offspring. Classification of parental investment into discrete r-selected and K- selected organisms does not reflect continuous range of life history strategies.

3. Key concepts Parental investment is costly but increases the probability of production and survival of young. Simplistic various reproductive strategies have evolved ranging from polygamy to monogamy.

4. Darwin’s Puzzle: Why are males and females different? Darwin, C. 1871. The Descent of Man and Selection in Relation to Sex. 1st ed., Murray, London.

5. Parental investment and sexual selection Trivers 1972

6. Assumption Assumption: every organism has adaptations that function to facilitate reproduction Members of a population/species live in the same environment, so why do some animals have different adaptations than others? Morphs: age, sex, others SEX: male and female adaptations are different WHY?

7. Parental investment “Any investment by the parent in an individual offspring that increases the offspring’s chance of surviving (and hence reproductive success) at the cost of the parent’s ability to invest in other offspring” (Trivers 1972)

8. Sperm vs. egg In sexually- reproducing species, the relative size of gametes define who is male and who is female.

9. Sexual dimorphism Amongst vertebrates, the clearest dimorphism is between gamete (sex cell) size. This single physical difference explains why behavioural sex differences exist. Females gametes: large, nutrient-filled, expensive to produce, limited in number, and produced infrequently. If fertilised this will lead to high costs to the female. Male gametes: small, have no nutrients, cheap to produce, constantly made throughout life. Reproductive Capability: females are thus classed as the ‘slow sex’ and males the ‘fast sex’.

10. Nurturant females In most animals, and almost all mammals, females provide far more parental investment than just the egg Internal fertilization protects, but at a cost Cod vs. gorillas Humans (mammals): – Prolonged internal gestation (pregnancy) – Placentation – Lactation

11. Female reproductive strategy Females have much to lose if they mate with the wrong male, they are thus selective about who they mate with. They look for certain criteria: Physical Features: size and strength which confer dominance and so preferential access to resources. Behavioural Features: may indicate willingness to invest or good parenting skills. Females will compete with other females for the right to choose the most desirable (alpha) males. They gain little from multiple matings and seek quality not quantity. Almost every reproductively capable female will be able to find a mate of some sort.

12. Male reproductive strategy Males are far less choosy as they as they little to lose and everything to gain if they can have as many mating opportunities as possible. Males are not tied to rearing offspring and so seek quantity. While they would prefer a superior female, they are less choosy. If presented with a sexual opportunity they will take it. Males compete vigorously with other males for access to fertile females. Male reproductive success is however very variable, a small number of males will achieve many matings, while many males may never mate.

13. Competitive males Males are fighting with each other to mate with as many females as possible More females = more offspring (sharp contrast to females)

14. Sexual selection and parental investment theory For members of the sex that invests more in offspring, reproductive success is limited by the amount of resources an individual can secure for itself and its offspring. For members of the sex that invests less in offspring, reproductive success is limited by the number of mates one can acquire.

15. Bateman’s Gradient Bateman (1948) observed that the number of offspring fathered by male fruit flies increased in proportion to the number of females with which the male had mated. Female reproductive success did not increase as her number of partners increased. This is 'Bateman's gradient' - the steeper the gradient the stronger is sexual selection. males females No. of mates No. of offspring From Anderson & Iwasa (1996) p 54.

16. Sexual selection and parental investment theory What of it? Selection acted on males differently than it acted on females Specifically, differences in parenting strategies cause differences in adaptations Sex that invests more: adaptations to survive and get resources for offspring Sex that invests less: adaptations to help them get as many mates as possible It explains why, in many species, males look and behave differently than females

17. Sexual selection and parental investment theory Explains primary sex differences (uteruses vs. testes) Explains secondary sex differences – Differences in weaponry (intrasexual selection) – Differences in ornaments (intersexual selection) – When the sexes have different adaptations, they are “sexually dimorphic”

18. r & K Selection r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus upon either increased quantity of offspring at the expense of individual parental investment, or reduced quantity of offspring with a corresponding increased parental investment, varies widely, seemingly to promote success in particular environments.

19. How many, and how often? r Selection (aka. Quick-and-many) K selection (aka. Slower and fewer) Age of maturation Young – usually before the next breeding season Older – usually many seasons after birth Number of offspring ManyFew Frequency of breeding Usually frequently (many times a season) – high fecundity = many eggs produced per breeding season Generally once a season. Low fecundity Size of offspring Usually smallGenerally larger Mortality rates High – many offspring do not live to sexual maturity Low – offspring generally survive Examples of species Mice, rabbits, most insects, cane toads, octopus, mass spawning organisms Humpback whales, elephants, humans, some birds

20. Eggs or liveborn young? OviparityViviparity Literally means Ovum = egg, parus = bearing Vivus = living, parus = bearing Description Eggs released by mother, embryos develop outside mother’s body, nourished by egg yolk Embryo develops in mother, born as young. Mode of nutrition varies Benefits Reduced energy use in care of young Yolk provides good nutrient source More likely for offspring to survive to birth Drawbacks Eggs may need to be incubated Less chance of survival to birth due to eg. Eggs desiccating, predators, poor environment Energy expenditure for female carrying offspring Examples Birds, sharks, reptiles, monotremes Humans, some snake species, most mammals

21. Oviparity Bony fish and frogs Birds and reptiles Known as -Amniote eggs Shell None, or leathery membrane Usually a hard, calcerious shell Benefits Wedge into safe crevices Better protected from desiccation – do not have to reproduce in water Dangers Desiccation Damage Cannot be hidden in crevices Examples Port Jackson shark, amphibians Hens, monotremes, crocodiles

22. Viviparity Egg yolk viviparity Placental viviparity Other source of nutrient More notes Cool habitat – kept warmer within body Largish eggs Any – nutrient sent via blood stream to embryo Very small eggs Feed them unfertilised eggs Feed them “uterine milk” – secretion from uterus Examples Some sharks and snakes. Sea snakes – so that they do not have to return to land to breed Mammals except monotremes, hammerhead shark Porbeagle shark (feeds with eggs), Bat rays (feed with “milk”) Types of viviparity are recognised by the nutrient source for the developing embryo

23. Porbeagle Shark - vulnerable They give birth to live young, which exhibit oophagy during gestation, that is, the developing young feed on unfertilised eggs, and female porbeagles can produce as many as 200,000 unfertilised eggs to serve this purpose. "Their large fins are used in traditional Asian shark fin soup..."

24. BAT RAYS – girl power During the mating season, males select a mate and determine her reproductive state by swimming closely behind her to detect chemical signals. Females help this selection process along by grouping together and offering up the suitable females. They protect the insuitable females in the middle of their group and these are the ones who are sexually immature or ones who have already mated.

25. Parental care or not? No parental care Care of laid eggs Care of young What is it? No contact with offspring after eggs are laid Guarding and/or incubating eggs to hatching Care of young after hatching/birth Benefits Free to mate more No energy expenditure Eggs have protection from predators/ harsh conditions High chance of offspring survival Drawbacks High levels of mortality Energy expenditure Some mortality after hatching Very high levels of energy expenditure – may not be able to mate for many years after offspring birth Examples Reef fish, frogs, turtles Seahorse, diamond python, cephalopods (eg. Octopus, squid), spiders Humans, primates. Mammals (milk), emperor penguins, emus

26. An interesting reproductive strategy…Naked Mole Rat (GADZ) http://academic.reed.edu/biology/professors/srenn/p ages/teaching/web_2006/Mole_Rat_cd_dtb/reproduc tive.html Naked Mole Rat information website including reproductive strategies

27. QUESTIONS Are they oviparous? Viviparous? R-selected or K-selected? What differences are there between the male and female reproductive strategies? What do scientists think is causing the difference between the breeding and non-breeding individuals? Physical differences between breeding and non-breeding females? What hypotheses are there as to the reason behind the ‘shoving’ between queen and worker mole rats?

28. Assessment task Choose two organisms to compare reproductive strategies (one r and one K selection) including: Comparison of investment in sperm and egg production – number, size, energy store. Parental Investment – number of offspring produced and by which method (oviparity or vivaparity), degree of parental care. Explain each organisms chance of survival in light of this information.

29. Courtship Key Areas: Sexual dimorphism as a result of sexual selection Male-male rivalry – large size, weaponry, sneakers Successful courtship behaviour in birds and fish can be a result of species-specific sign stimuli and fixed action pattern responses. Imprinting is an irreversible developmental process that occurs during a critical time period in young birds and may influence mate choice in later life. Females are generally inconspicuous, reversed in some species. Female choice: Assessing male fitness Fitness can be in terms of good genes and low parasite burden. Lekking species – alternative successful strategies of dominant and satellite males.

30. Learning Activity F - COURTSHIP Research and make brief notes on: 1.Male-male rivalry and courtship behaviour 2.Female choice – assessing male fitness 3.Imprinting behaviour 4.Leking species – strategies of the dominant and satellite males. Use the following web-links to help you:

31. 1. Male-male rivalry and courtship behaviour http://www.bbc.co.uk/nature/adaptations/Courtship_ display http://www.bbc.co.uk/nature/adaptations/Courtship_ display Selection of videos showing examples of courtship behaviour. http://www.arkive.org/red-deer/cervus-elaphus/video- 09d.html http://www.arkive.org/red-deer/cervus-elaphus/video- 09d.html Videos showing red deer male-male rivalry http://www.janegoodall.ca/about-chimp-behaviour- social-organization.php http://www.janegoodall.ca/about-chimp-behaviour- social-organization.php Information about chimpanzee courtship behaviour in a dominance hierarchy

32. 2. Female choice – assessing male fitness http://beheco.oxfordjournals.org/content/15/2/239.full Article from Behavioural Ecology: Female mate assessment and choice behavior affect the frequency of alternative male mating tactics Author: Barney Luttbeg http://www.medsci.uu.se/digitalAssets/21/21196_3.pdf Fitness effects of female mate choice: preferred males are detrimental for Drosophila melanogaster females Authors: U. FRIBERG & G. ARNQVIST

33. 3. Imprinting behaviour http://www.britannica.com/EBchecked/topic/ 284209/imprinting http://www.britannica.com/EBchecked/topic/ 284209/imprinting http://www.cerebromente.org.br/n14/experi mento/lorenz/index-lorenz.html http://www.cerebromente.org.br/n14/experi mento/lorenz/index-lorenz.html Learning Who is Your Mother - The Behaviour of Imprinting Authors: Silivia Helena Cardoso and Renato M.E. Sabbatini

34. 4. Leking species – strategies of the dominant and satellite males http://birding.about.com/od/Bird-Glossary-L- M/g/Lek.htm http://birding.about.com/od/Bird-Glossary-L- M/g/Lek.htm Definition of lek. http://www.bbc.co.uk/nature/life/Black_Grouse Videos/Information about the black grouse which exhibits leking behaviour https://www.youtube.com/watch?v=AAXf4UMYn oI https://www.youtube.com/watch?v=AAXf4UMYn oI Video showing black grouse lek

35. Read the example of an ethogram and time budget – notes task What is meant by an ethogram? A time budget? Write a set of instructions for contructing your own ethogram and time budget.