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Biology 3436F/G L16 &17.docx

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Biology 3436F/G
Tom Haffie

Lecture 16 & 17 Parental Care Sexual Selection A form of natural selection that occurs when individuals vary in their ability to compete with others for mates or to attract members of the opposite sex How do individuals compete for mates? (intrasexual)  Fighting which leads to evolution of antlers or claws (gain access to territories or mates)  Forming dominance hierarchies Barnswallows have biparental care (chicks would die without care form both parents) How do individuals advertise their attractiveness (intersexual) Cichlids suck up larvae in mouth to protect them from  Songs (birds) and dances predators. A lot of defense involved; young can feed on their own so do not need parents help Summary Parental Investment (Trivers) 1. There is variation in mating systems among animals 2. Bateman’s Principles reveal a difference between Any investment by the parent in an individual offspring that males and females in benefits to multiple-mating increases the offspring’s chance of surviving (and reproducing)  Males ben = lots of mates at the cost of the parent’s ability to invest in itself or other  Female ben = lots of resources offspring 3. Sexual selection involves competing for access to mates and attracting mates. In terms of sexual selection can invest 3 ways:  Parental effort (parental investment) Parental Care  Mating effort (attracting mates  Kangaroo  Gametic effort (effort in producing gametes) o Young depend on mom for food o Yong develop quickly; crawl into pouch andParental Care drink milk  Includes metabolic investment in the primary sex cells o Parental care very important in kangaroo  Dung beetles (gametic effort)  Does not include effort in finding a member of o Role feces into ball to attract females o Eggs laid in ball and feed of resources opposite sex or subduing a member of its own sex (mating effort) o Direct benefit to choosing male who produces biggest ball Costs and Benefits of Parental Care o Parental effort; more resources and mating effort; stronger males Benefits  Increased hatching  Increased growth  Reduced predation  Increased breeding success’  (Benefits measured from offspring perspective) Costs  Energy  Time Lecture 16 & 17 Parental Care  Increasing predation (adult) Patterns of parental care Patterns of Parental Care Typically fish have no parental care. The care we  Decreased breeding success see is predicted by the type of fertilization we see. Fish External fertilization usually results in male care.  (Costs measured from parental perspective) Internal External FertilizationFertilization Male care 2 (9%) 61 (33%) Female care 14 (67%) 24 (13%) No care 5 (24%) 100 (54%) Gross & Shine (1981)  Typically fish have no parental care  Care seen is predicted by type of fertilization Survival of offspring is much higher when mother is present.  External fertilization  male care usually Also receive less aggression from other members when mom Patterns of parental care present Three hypotheses for general patterns: Three Hypothesis for general patterns: 1.Paternal certaintyty Males should be more confident in their paternity when eggs 2. Order of gamete release are fertilized externally since fertilization occurs at time if oviposition  uniparental male care will evolve 3. Association  Except in blugills (cuckoldry decreases certainty) 2. Order of gamete release Low levels of fanning leads to low levels of hatching success. Internal fertilization gives the male a chance to leave prior to Where male quality is low there is high predation (depends on fertilization  uniparental female care how fat? They have to scare off predators) External fertilization gives females chance to leave What is “opportunity cost”? Types of Parental Care  Many exceptions in fish, frogs, shorebirds (external— female care) 3. Association Association with the embryos preadapts a sex for parental care  Eg. Internal fertilization should lead to female care BUT no necessarily uniparental care  Monogamy should lead to biparental care (already Shows transition between different paternal care together)  high % of species have no parental care (predict “Preadapt” feature that evolves to create conditions favorable ancestral stage) for another adaptation  May become uni-parental male/female  Association is best hypothesis to explain general Biparental care usually evolves from uniparental male pattern of parental care care o The conditions that lead to parental care patterns o What are the costs and benefits that lead to some species providing care and others not Lecture 16 & 17 Parental Care Opportunity Cost Birds – biparental care The most valuable option that was foregone to perform a particular behavior Eg. A hypothetical students opportunity cost of attending a review session before an exam is 1 hour of independent study time Mammals – uniparental female care Both parents have low opportunity cost to care  Food increases with additional parent  Single parent defends nest and can’t spend much time foraging  With an additional parent there is more time to forage resulting in many more offspring Recognition Systems and Parental Care Female mammals pay lower opportunity cost to parental care  (High degree) Cuckoldry should lead to reduce parental investment Rate of producing offspring as a function of body size  Bluegills can recognize their relatives; they were  Gain very little by growing bigger
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