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Chapter 10-11:Sex and Mating

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1 Chapter 10-11:Sex and Mating
Name: ________ Period: _____

2 Females' sex organs look identical to males'
Can you look at another member of your species and tell whether it has an egg or lots of sperm cells to merge with your DNA? Larger Females Females' sex organs look identical to males'

3 Asexual reproduction No exchange of genetic material. Involves only ONE parent. Offspring is a CLONE of parent (same DNA) Sponges and coral reproduce asexually by “budding” Parthenogenesis: Type of asexual reproduction where a female’s eggs develop into offspring without ever being fertilized by a male! “Virgin birth” Ex: some fish, insects, and a few species of frogs and lizards Komodo Dragon Hammerhead shark

4 Sexual reproduction What defines reproductive success?
Combination of genetic material from TWO parents What defines reproductive success? 1. ability to produce healthy offspring ability to spread your genes Females Males Limited number of eggs (400 human life) Gestation period (takes time) Estrus period (sexual receptivity) Parental care If she fails, she must wait until next year to try again! Menopause Therefore, females spend substantially more time and energy in reproduction…more to risk. Unlimited sperm production 100’s millions per ejaculation! Sexual success is to fertilize as many females as possible. Contribute nothing more than GENES. ** Results in SEXUAL CONFLICT = (males and females acting differently)

5 Sexual conflict Natural Selection
Males spend substantially more time and energy competing against other males for potential mates. Consequently, males are usually larger and more aggressive. This is called Sexual Dimorphism…Males and females looking differently. It is caused by Sexual Selection… different traits affect each sex differently peacock Lion pheasant Natural Selection In areas of high competition, sexual dimorphism is high. In areas with low competition, sexual dimorphism is low

6 Reproductive advantage
An adaptation or trait (physical or behavioral) that allows you to reproduce. Ex: A peacocks bright feathers attract a female. * Does not necessarily mean increased survival advantage!! (which is why we like “reproduction of the fittest”) * Ex: A brightly decorated peacock is more easily seen by predators!! * Reproductive potential outweighs risk of predation!

7 Intrasexual selection
(within one sex) Members of one sex (usually male) compete for mates. Common for herding animals Male secures a herd of females and aggressively defends his “harem”. Males can impregnate 100’s of females, therefore high competition for females….it’s worth the risk of injury! High success for alpha males Females “synchrony” determines whether the male will protect the females all year or just during the mating season Sexual Selection: Males are larger and better able to fight and defend Natural Selection: Females are larger and better able to produce, store, carry, and provide resources for eggs.

8 Male elephant seals are up to four times larger than the females and are extremely aggressive to defend a harem of about 30 females, all in a large group on a beach.

9 5. Dual Male Forms (phenotypes)
What about the “little guy? What about the Beta and Gamma males and their genes? Other evolved behaviors include… 3. Guarding / Repelling Males stays with female the whole time to ensure his sperm’s “safety”. * Some butterflies leave a repellant smell on the female so no other males will mate with her! 1. Female Mimicry “pretend” to be a female. Sneak into harem and mate. Alpha male cannot attend to ALL females all the time! 2. Satellite Male Beta male hangs out on the edge of territory and “intercepts” females as they enter 4. Sperm Competition Some male insects have a devise on their penis to remove existing sperm from other males. Some can seal up the female genitalia = chastity belt!! Mimic female; get other male to release sperm 5. Dual Male Forms (phenotypes) Coho Salmon either large aggressive or small docile. The balance each other out and are perfectly stable. If more large ones, they would fight over territory too much and small ones would thrive. If more small ones, the big ones wouldn’t fight and would dominate the small ones. Both strategies equally successful

10 Intersexual selection
Female chooses her mate. Competition among males exists, but not fighting or aggression Bases her choice on a trait she finds attractive. Males make sounds, visual cues, or give gifts to gain her attention Females have much to lose, so they should be picky when selecting a mate! Male may not be the best male, but rather the one with the best territory, or builds the best nest, or brings the biggest piece of food. Results in: Courtship rituals ~ male and female perform together Courtship displays ~ one sex performs for the other. bowerbird displays

11 Functions of Courtship
Identification – ensures mating is with the same species Reduce aggression – some larger females may recognize the smaller males as a threat and attack. His display will prove his ID and calm her down (often times he gives her a gift of food). Fitness assessment – size up the potential mate. Mating readiness – ensures she is physiologically ready for sex…is she ovulating? 5. Bonding – some animals need to ensure their compatibility with their partner

12 Lek displays A Lek is a gathering area for males to “perform” for a female’s attention. Males gather to dance, call, or display their talents (no fighting) Center of the Lek is reserved for dominant males Frogs and toads = chorus

13 Hemaphroditism Sex Change Protandry: born male, then change to female
Possess both male and female organs Can exchange sperm and egg simultaneously Self fertilization rarely occurs Usually found in solitary, slow-moving animals ~ difficult to find a mate ~ therefore, everyone is a mate! Sex Change * Occurs in animals with simple sex organs ONLY and external fertilization. Not possible in mammals that have placenta, nipples, uterus, live young, etc. Protandry: born male, then change to female Protogyny: born female, then change to male Clown fish grouper

14 4 major mating systems 1. Monogamy – exclusive one male and one female
2. Polygyny – one male mating with several females Polygamy 3. Polyandry – one female mating with several males 4. Polygynandry – both sexes having many partners Are these patterns genetically programmed in each species?

15 Monogamy relatively rare in nature (only 3% mammals are monogamous)
common where resources are low and offspring are helpless common in rodents, but mostly found in birds - helpless until flight functional for nest protecting and food gathering when both parents invest, higher survival rate for offspring name a species that will only mate in private? Can you suggest a reason for this unusual behavior? Swans and geese stay together for life, even when not breeding! * Extra pair copulations is a common behavior for monogamous couples

16 Polygyny one male mating with several females 4 types:
when food is plenty, and competition and predation are low, monogamy is not necessary. advantageous for males because, unlike female, he can increase his reproductability, he has no gestation period, and does not lactate. most common mating system in the animal kingdom (97% mammal) 4 types: Resource defense 2. Female Harem Defense 3. Male Dominance 4. Scramble Competition Female’s reproductive success depends on availability of resources – food, water, safety Females gather in defendable areas – benefits from mutual defense, alarm calls, and safety. Resources are plentiful and NOT clumped. Females are free to choose whomever she wants…such as males that are most FIT. Lek systems Study: 6% of bats did 80% of the mating Males actively search for females, but with little competition or fighting. Usually large groups of females and large groups of males gathering together…fighting unnecessary. Fleshman response: Male curls lip upward and smells female genitalia to determine if she is sexually ready. Common in hoofed mammals Small territory – single male ~ elephant seal Large territory – few males ~ lions, chimps

17 Polyandry One female mates with many males Very rare in nature
Few birds, insects, sea horse Female success is how many males she can mate with Female will lay many clutches of eggs for males to incubate Males have small territory, while female has larger territory encompassing many males areas (jacana bird). She will breed with ALL the males!

18 Polygynandry (promescuity)
Multiple mating pairs for both sexes. A combination of polygynous males and polyandrous females Usually occurs when male territories overlap, and each contain at least one female. A Male weasel will travel to find females. He will mate and continue to travel. The females will mate with many traveling males, and the males will mate with multiple females along his travels.

19 Mating Terms (mammalian)
Courtship: male sniffs and performs for the female. Recognition. Pursuit: Male chases the female Mounting: the male mounts the female Lordosis: arched back posture with tail to the side. Invites insertion Intromission: penis insertion Ejaculation: occurs after multiple intromissions (thrusts) Rest: refractory period for males. “Coolidge Effect” – refractory period in lab rats is decreased (or eliminated) if different female is introduced! Named after President Calvin Coolidge.

20 Sex As defined by William Masters and Virginia Johnson (1957)
Researched sex - best seller, translated into 30 languages Masters and Johnson Institute, St Louis Defined 4 stages of sex: 1. Excitement 2. Plateau 3. Orgasm 4. Resolution Vasocongestion: increase blood flow to tissues (swelling), including face, cheeks, and lips. Also causes fluids to seep through = lubrication. Increase in BP, HR, and pulse. Scrotum pulls toward body. Labia majora flattens, minora swells and opens. Cervix and uterus retract creating room for penis insertion. “Sex Flush” in females – redness Breathing, pulse, bp, and hr increase dramatically. Muscular contraction across body, including face Rhythmic muscular contractions of genitalia, including vagina, uterus in females and urethral bulb (prostate) and penis in males. Excitement and plateau reverse. Body returns to unaroused state Decrease in muscle tension Males have refractory period where they cannot become erect or orgasm. Ranges from minutes to days. Females do not experience this Vasoconstriction peaks Breathing, pulse, bp, and hr increase Breasts swell Clitoris retracts into body Labia darkens

21 Physiology of sex Nitric oxide: increase blood flow to penis (viagra targets this chemical) Serotonin: contract smooth muscle in genitalia Epinephrine: increase muscle contraction during sexual activity, increase vaginal pulse amplitude. Dopamine: “pleasure chemical”. Responsible for sexual arousal. Prolactin: reduces sexual desire (after sex). Inhibited by dopamine, and effects dopamine release (too much causes impotence) Androgen: primary male hormone (testosterone). Causes sexual desire. Made by the sex organs. Estrogen: primary female hormone. Does not cause desire, but leads to lubrication during sex. Progesterone aids the female libido (not estrogen). ** Can males “smell” estrogen from female? May cause instant sexual arousal. ** Most sex hormones are controlled by thalamus, hypothalamus, and pituitary in the brain.

22 Menopause “Reproductive cessation” Experienced in females only
In humans: - Lower estrogen levels leads to thinning vaginal walls and labia, and decrease in lubrication…sex can be painful. - Usually occurs in women about 50 years. High sexual activity during this time can reduce the symptoms. Can also be treated with hormone therapy. - Menopause does NOT occur in males, however, aging men experience shrinking testicles, decreased sperm count, a reduction in volume and force of ejaculation, and a longer refractory period. Erectile dysfunction (ED) is common. - People over 70 years old: 65% women and 59% men still sexually active.


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