ECOL 182R 1st Edition Lecture 3 Outline of Last Lecture I Population species A Problems of interbreeding II How new species form A Isolation B Divergence III Speciation rates Outline of Current Lecture I Adaptive behavior A Four F s of Behavior B Sexual and asexual II Why is sex so common A Inbreeding III Male female differences A Patterns B Sperm egg IV Animal reproductive behavior A Choosing mates V Plant reproductive behavior A Choosing mates Current Lecture Adaptive behavior Animals plants both exhibit the Four F s of Behavior Feeding Fighting Fleeing Reproducing Asexual vegetative reproduction uses genetic info from 1 parent only Produces offspring identical to parents and to each other Ex Cloning Parthenogenesis within the female purely esexually Ex Binary fission no sex involved there s one then there s two Faster than sexual more efficient less risky Sexual combines genetic info from 2 parents Produces offspring different from parents and from each other More costly than asexual much more risky They show their courtship and usually rejected ignored Often aren t feeding while mating Parental care is time consuming Big risk of not finding mates Then why is sex so common in nature It s a biological mystery but what we know 1 Environment varies in space time Big benefit to making variable offspring at least a subset should succeed Evidence 1 Genetically uniform crop plants are at a disadvantage can be great for yield but you aren t allowing them to sexually reproduce If there s a disease invasion that is good at attacking that strain of crop it ll wipe out everybody Ex Irish Potato Famine Evidence 2 Animal cloning Keeping them from having sex Dolly first cloned sheep dead 2 Sex leads to recombination which repairs damaged DNA Even sexually reproducing organisms experience some of the costs benefits of asexuality Not all sexual reproduction involved outbreeding mating with an unrelated individual Inbreeding mating with yourself or a very close relative Since the mate is genetically similar to you there s little advantage to exchanging genes with it plus it can bring out harmful recessive alleles So many adaptations act to reduce the likelihood of inbreeding because of those problems Outbreed it better than inbreed but inbreed is better than no sex at all How are males and females different Within species reproduce behavior of males and females often differs greatly Males initiate courtship and fight for access to females Females don t fight for males and often reject courting males So why is it a pattern at all then Sperm are really small and cheap to make Eggs are large and expensive to make Males can increase their success by having MORE mates and females can increase their success via HIGHER quality mates not more of them Animal Reproductive Behavior Poses two problems 1 How to locate mates in the first place 2 How to choose among them How to locate mates For the Great Tit bird in England 1 Go looking One sex often leaves home to search for mates before their first breeding attempt Inbreeding avoidance The young females disperse Only 1 of 885 observed end up inbreeding 2 They become easily found A Lek is a communal conspicuous area where males display to females So she just goes looking for a lek Some insects use Chemical Signalling Females moths release chemicals or pheromones that males detect follow Choosing among them Females choose males who 1 Can contribute good genes to young 2 Control useful resources 3 Contribute good parental care in some species Ex Female bullfrogs choose males with large territories Males do best by convincing females that they have the right stuff whether it s true or not How 1 Strenuous dances jumping spiders 2 Present gift of food another kind of spider go kill something wrap it in silk present it 3 Defend a large territory bullfrogs 4 Be elaborate bright peacocks Why do females care about the brightness and long tails Because it shows they re healthy don t have a parasite showing the male is strong enough to carry such a long tail etc Traits like these evolve via sexual selection the spread of traits that confer a mating advantage It s a form of natural selection In Cardinal birds Males have undergone natural selection for a mating advantage with their bright red color females have undergone natural selection for being hard to see they blend in Mating is a form of cooperation But Males fool females those spiders can just make an empty package that s huge and attractive Females fool males pretend they want to mate then just eat them instead Non trivial points 1 In some species the usual sex roles are reversed For the Red Phalarope bird females are larger than males and males incubate the eggs Great research question what makes this type of bird do it reversely 2 We ve begun to discover an incredible diversity of normal mating behaviors in the natural world Two females form life long bond it happens same sex bonding Can animals be gay 3 Human behavior is shaped not only by sexual election but culture Shopping malls are leks Plant reproductive behavior Like animals plants 1 Face problems finding choosing mates 2 Have choosy females 3 Experience sexual selection BUT unlike animals most plants don t have two sexes Then what are the types Dioecy individuals are either males or females Monoecy individuals are both male and female Whether they have both male and female parts or on one plant there are both male and female flowers budding from it So the entire plant is both male and female How do they locate mates 1 Pollinate yourself only in monoecious plants obviously It s efficient but inbreeding is costly and you lose the opportunity for a sexually reproducing event And some plants do it only as a last resort 2 Pollinate someone else How does pollin get somewhere Either abiotic pollination water or wind carried but they have to make a TON of it because delivery is imprecise But there s always water and wind so that s nice OR biotic pollination an animal picks it up and moves it The delivery is precise but the animal must somehow be attracted to the plant and fed Once they locate mates how does female choose 1 Female can prevent pollen from fertilizing the ovary 2 Only allow best males to fertilize 3 Abort ovaries fertilized by poor males These traits will evolve via sexual selection