CHAPTER 8 ACHIEVE, HW, SUMMARY

Classify the statements about asexual and sexual reproduction as true or false. ALLELES FROM ? (2_ GAMETES REDUCING SEXUAL REPRO)

True FALSE-SEX REPRO IS PARENT PASSING TWO GENE SETS TO OFFSPRING ASEX MAY BE FROM PARENTS VEGETATIVE/NONSEXUAL TISSUE IN REPRODUCTION Habitual self-fertilization by hermaphroditic individuals is a sexual route by which genetically identical individuals can arise.-->self fertilizing and outcrossing are sexual rpeodduction for them? Asexual reproduction is the simplest mode of reproduction. Asexual reproduction most commonly refers to instances in which a single parent copies its DNA directly into all of its clonal offspring. COMMONLY TALKING BOUT CLONING Organisms may also reproduce asexually via parthenogenesis, which can produce full clones that contain all of their parent's DNA, OR HALF clones that undergo some meiosis. Asexual reproduction is efficient and can occur using reproductive tissue, such as egg cells, or nonsexual tissues, such as the stems or roots that produce vegetative growth in plants. Sexual reproduction involves combining male and female gametes in a process known as fertilization to create embryos. Typically this occurs when two separate individuals combine their gametes, but some organisms can produce both male and female gametes on their own. (HERMAPHRODITES CAN DO THIS) These organisms, called hermaphrodites, can self-fertilize to produce offspring. Sexual reproduction often requires more TIME and ENERGY than asexual reproduction. Sexually reproducing organisms may engage in costly and risky courtship behaviors, such as territorial aggression or offering nuptial gifts, to secure a mate. MEIOSIS COSTLY AND SLOWER THAN CLONING An asexual organism does not spend time or energy finding and attracting a mate. However, mutations ACCUMULATE every time DNA is COPIED. Asexually reproducing species that have NO way to RID themselves of DNA mutations may be at greater risk of extinction than sexually reproducing organisms, which have a chance of purging harmful mutations with each generation. In either form of sexual reproduction, out‑crossing or self‑fertilization, DNA from male and female gametes combines to produce offspring with slightly different combinations of alleles. Combining ALLELS from two gametes gives sexually produced offspring a chance of avoiding harmful mutations carried by their parent or parents. Mutations that, by chance, are not passed to the offspring are purged with each generation HARMFUL ALLLE INHERIT BY SOME OFFRPSING OF SEX REPRO siblings don't always just share 50% DNA with each other from asexual repro costly/risky behavior from sexually repro animals

ANIMAL DIF BW HAPLOID CELLS VERSUS PLANT AND FUNGI . When progeny inherit DNA from two parents through the ? of two gametes, we say they are the result of sexual reproduction

UNIION GAMETES, SEX REPRO Haploid germ cells, called gametes, are produced through meiosis within sex organs called gonads. In animals, these haploid cells can immediately act as gametes. In plants and many protists, the haploid cells develop into MULTICELLCULAR haploid STAGES of the life cycle that eventually produce gametes. During meiosis, the distribution of the chromosomes into COMBINED DIPLOID CELL the gametes is generally random and the subsequent mixing of chromosomes from the two parents results in new combinations of genes in the offsprin--> fertilization to produce a diploid zygote.

STRATEGIES IN MIXED-MATING

When a mate can be found, the individual prefers to breed by outcrossing to avoid the costs of inbreeding. When a willing mate cannot be found, the individual self-fertilizes OUTCROSS VERS SELF FERT the self-fertilizing individuals can benefit by avoiding the cost of meiosiS if mutations were eliminated On the other hand, if deleterious mutations have been purged in the population due to past inbreeding, Attracting mates can be energetically expensive, as is the case with plants that must produce NECTAR to ATTRACT pollinators. orange jewelweed,, As a result, these plants produce a higher proportion of selfing flowers, Plants that experience herbivory of their leaves have less energy to make outcrossing flowers.

What is the difference between simultaneous and sequential hermaphrodites?

When male and female structures function at the same time, we call it a simultaneous hermaphrodite.-->GAMETE PROD FROM BOTH SO EGG SPERM SAME TIME , PLANTS HERMAPHS-->mollusks, WORMS, and plants When an individual possesses one sexual function and then switches to the other, we call it a sequential hermaphrodite. Examples of sequential hermaphrodites are some species of mollusks, echinoderms, fishes, and plants.

When females choose mates, why might extreme secondary sexual traits in males be good predictors of mate quality?

All adult males exhibit the secondary sexual traits of their species. Females that use these traits to choose a mate compare one male's display to that of other males. Secondary sexual traits can indicate that a male has other important heritable traits, such as a robust immune system or skill at finding food Males that survive despite the handicap of an extreme trait may signal that they are healthy and have good genes. In species with extreme secondary sexual traits in males, females appear to judge the quality of the trait when choosing a mate. For example, male peacocks produce massive tail fans and display them to attract females. Males with the best displays, according to the females, mate more often than other males. Extreme traits handicap the male by making it more difficult for him to hide from or escape predators. Research suggests that an extreme trait may give the females accurate information about the male's health and the quality of his genotype. Superior males survive despite the handicap of the trait. Extreme secondary sexual traits tend to evolve in species in which males do not defend a nesting territory or contribute anything other than sperm to their offspring. Since females of these species raise their young without help, the females improve the chances of their offspring surviving by choosing males with superior genes as mates. All adult males develop the secondary sexual traits of their species regardless of their health. However, the quality of the extreme traits varies between males. 'handicap principle' proposes that females prefer males with handicaps (mating characters that reduce survival chances) because handicaps are indicators of heritable viability.

In terms of broad categories, we can consider two types of female preferences: ? benefits and ? benefits.

MATEIRAL BENEFIT a site for raising offspring and resources for producing eggs and feeding her offspring should improve a female's fitness. For example, males of the black-tipped HANGINGFLY (Batticus apicalis) capture dead insects and present them to the females as a food item LARGE FOOD=LONG MATE nonmaterial-->CHOOSING FROM TRAITS, INCLUDES the good genes hypothesis It has been more of a challenge for scientists to understand female choices when the female does not receive any material benefits from males widowbirds (Euplectes progne), a small, polygynous species that inhabits the open grasslands of central Africa. In contrast, during the breeding season, males are jet black with a red shoulder patch, and they sport a half-meter-long tail that is conspicuously displayed in courtship flights (Figure 8.24a). The most successful males may attract up to a half dozen females to nest in their territories, but the males provide no care for their offspring. clipped feather ends onto the feathers of the tails of other males to lengthen them. As you can see in Figure 8.24b, males with experimentally elongated tails attracted significantly more females than those with shortened or unaltered tails. Long-tailed widowbird. (a) During the breeding season, males have exceptionally long tails. There are two possible hypotheses. According to the good genes hypothesis, an individual chooses a mate that possesses a superior genotype. In the gray treefrog, for example, females prefer males that can produce the longest mating calls. Long calls can only be produced by the largest and healthiest male frogs. If male size and health have a large genetic component, choosing this trait might benefit the female's offspring they found that the offspring of long-calling males grew faster than the offspring of short-calling males. S INDEEED HEALTH GENETIC COMP

progeny produced by asexual reproduction inherit DNA from a single parent. This can be accomplished through either ? or parthenogenesis. EX OF EACH

vegetative reproduction Vegetative reproduction occurs when an individual is produced from the NONSEXUAL TISSUES of a parent LIKE NEW SHOOTS leaves, roots, or rhizomes VEGETATIVE , walking fern (Asplenium rhizophyllum), which produces offspring when the TIPS of its leaves TOUCH the SOIL placed a plant clipping into a glass of water and watched it grow roots to become a new plant Individuals that descend asexually from the same parent and bear the same genotype are known as clones-->BODY BUDS=NEW INDIVIS duplicating their genes and then dividing the cell into two identical cells, a process known as binary fission. Since, progeny plants arising by vegetative reproduction are identical to their parent plants, hence, they can be designated as CLONES VEG REPRO MAKING CLONES?.

In a population of snails occupying a single small pond, some individuals possess a single sex and some individuals are simultaneous hermaphrodites that are capable of reproducing with both males and females. After monitoring the snail population for several years, you find that an average male-only pond snail produces 50 offspring per week during the peak of the reproductive season, while an average female-only pond snail produces 40 offspring per week during the same period. In addition, the average hermaphroditic pond snail produces 30 offspring using its male function and 30 offspring using its female function per week. What is the order of these three reproductive strategies, from lowest to highest, in terms of their relative fitness?

hermaphrodite < male < female THINK ITS WRONG

COPIES OF GENES IN EGGS: ASEX, SEX, HERMAPH, WHAT ELSE CAUSES OFFSET

If two hypothetical female organisms can only produce four eggs, (a) the female that uses asexual reproduction contributes eight copies of her genes. PUT TWO CHROM COPIES INTO EACH EGG A hermaphrodite can pass on eight copies of its genes by producing four eggs that are fertilized by another individual's sperm and four copies of its genes when it uses its sperm to fertilize another individual's eggs. Such an individual can contribute one set of its genes to offspring produced through female function and another set to offspring produced through male function. As shown in Figure 8.4c, this allows a hermaphrodite to contribute twice as many copies of its genes to its offspring than is possible for an individual that can be only male or female. GIVE GENES TAKING ON EACH ROLE, DOUBLE THAN IF USING DIF GENDER , PRODUCE GAMETES IN EACH FUNCTION0-->COST MEIOSIS counterbalanced in hermaphrodites The cost of meiosis can also be offset when an individual is either male or female and the MALE helps the female take CARE of the offspring. INCREASE NNUM OFFPSRING THAN ONLY MALEt

In most species containing individuals that are either male or female, the proportion of males and females changes over time. Based on the data shown in the graph, select the statements that describe what happens whenever one sex becomes rare or common.

In cases where the sex ratio deviates from equality, parents producing the rarer sex will have higher fitness because their offspring will have a higher probability of finding mates and reproducing. Alternatively, parents producing the more common sex will have lower fitness because their offspring will have a lower probability of finding mates and reproducing. Thus, the rarer sex will increase in frequency. This is called frequency‑dependent selection, and it explains why most species have one‑to‑one sex ratios. The ratio of males to females is only occasionally close to one‑to‑one, and deviations from this sex ratio are found in many of the years in this data set. When one sex becomes rare, parents producing that sex have higher fitness due to a higher probability of mating success in their offspring. The rare sex becomes more common. When one sex becomes common, parents producing that sex have reduced fitness due to a lower probability of mating success in their offspring. The common sex becomes rarer.

asexual populations benefit by having more ? reproduction and avoiding the cost of meiosis, asexual clones cannot persist in the face of high rates of ?. As a result, the asexual snails do not survive well in the shallower regions of the lake, where they are more likely to encounter the parasitic worm.

asexual populations benefit by having more RAPID reproduction and avoiding the cost of meiosis, asexual clones cannot persist in the face of high rates of PARASITISM. As a result, the asexual snails do not survive well in the shallower regions of the lake, where they are more likely to encounter the parasitic worm. When they introduced a pathogenic bacteria, they discovered that the asexual worm populations went extinct after 20 generations. In contrast the sexual populations persisted for more than 30 generation REASON=CONTINUED RESISTANCE EVOLVED IN POPL

IN GENERAL MATING INVOLVES

mating systems often involve ATTRACTING a mate or DEFENDING against other members of the same sex

In a tropical plant species, one individual FEMALE MATES with a male and produces 1,000 offspring. Another individual exhibiting hermaphroditism is capable of reproducing sexually with males but also possesses male reproductive organs that allow it to reproduce sexually with OTHER females. If a hermaphroditic individual also produces 1,000 offspring, how many MORE total copies of each gene will the hermaphrodite pass on to its offspring than the female that is capable of reproducing only with males?

1,000 The hermaphrodite would contribute half of its genes each time it reproduces, whether it does so as a male or as a female.-->BECAUSE SEXUAL REPRO 0 SAME AMT FOR SEXUAL REPRO

Each vegetatively reproducing individual belonging to coral species A produces 250 offspring during each reproductive event. Typically, in coral species B, whose individuals always reproduce sexually, a single individual will produce 500 offspring. However, a mutation has arisen in one particular species B female that causes her to contribute only half as many copies of her genes to her offspring as she normally would. How many offspring would this female have to produce to pass along the same number of her genes to the next generation as an individual of coral species A?

1,000 offspring-->500 GENE COPIES FROM A

Which parent will pass the largest total number of its genes on to its total offspring?

A-1500 B-1200 a haploid parent that produces 750 offspring via parthenogenesis Since the parent is haploid, this would only result in 750 copies of its genes a diploid parent that produces 750 offspring via vegetative reproduction-->1500 , NO MEIOSIS

OTHER ENVIRO SEX DETERM EXAMPLES

As mentioned in our discussion of SEQUENTIAL hermaphrodites, the blue-headed wrasse is a coral reef fish that is able to change from female to male as it ages headed wrasses typically begin life as females and live in large schools along with one or a few dominant males. One benefit of this strategy is that the young fish, by being female, will not have to fight with the dominant male. . If the dominant male leaves or dies, however, the largest female will then change sex and become the new dominant male. Being large is important for males, because they must defend a territory

Under what conditions would natural selection favor the evolution of polygyny? Under what conditions would natural selection favor the evolution of polyandry? What behavior can a mate use to enforce monogamy? SELEC OF NOT JUST SEX RATIO BUT?

Because of this size difference, female and male reproductive strategies are also different. A female's reproductive success generally depends both on the number of eggs she can make and on the quality of the mates that she finds. Because most males can produce millions of sperm, a male's reproductive success generally depends on how many females he can fertilize ENERGY DIF IN SPERM MEANS DIF STRATEGY Like sex ratios, the mating system of a population is subject to natural selection. Consequently, mating systems are often a product of the ecological condition MATING SYSTEM Consequently, mating systems are often a product of the ECOLOGICAL CONDITIONS under which species live. Figure 8.18 illustrates examples of the four mating systems: promiscuity, polyandry, polygyny, and monogamy. PROMISCIUITY occurs in species of outcrossing PLANTS such as the prairie sunflower (Helianthus petiolaris). Polygyny exists when a male mates with several females, as in elk (Cervus canadensis). Polyandry occurs when a female mates with multiple males, as is the case for the western toad (Anaxyrus boreas). Monogamy for life was thought to be the rule in 90 percent of all birds, as in the sandhill crane (Grus canadensis). However, recent genetic analyses have confirmed that most bird species actually participate in extra-pair copulations.

Many bird species engage in social monogamy but copulate with multiple individuals. How have these extra‑pair copulations influenced the evolution of mate guarding in socially monogamous species?

Extra-pair copulation promotes mate guarding because the male partner of a monogamous pair does not benefit from rearing an unrelated chick. Socially monogamous birds mate as pairs in which both sexes provide care for each nestling. Every chick in the nest is related to the female partner. If the female engages in extra-pair copulation, some chicks in the nest may be unrelated to the male partner of the social pair. Both partners benefit from having more genetic variation among their offspring, but the male does not benefit from rearing offspring unrelated to himself. In socially monogamous birds, selection favors males who spend energy to prevent their partners from mating with neighboring males. Because a monogamous male does not receive a fitness benefit from providing resources for offspring that he did not sire, selection favors protective behavior in the male. Socially monogamous females tend not to exhibit mate guarding because all of the offspring in the nest are biologically related to the egg‑laying female. The female bird can produce as many biological offspring with a single male as she does with multiple partners, and all of them are related to her. A male benefits from promiscuous behavior because he can sire offspring in multiple nests while only providing care for a single nest. However, he cannot guard his own mate while he mates with other females and may rear another male's offspring as a result. Thus, extra‑pair copulations favor mate guarding behavior when males provide care for offspring. DOESNT WANNA MISS IT AND GIVE RESOURCES TO BIRD HE DOESN'T KNOW ISNT HIS

What adaptations have evolved in plants that would help monoecious plants prevent inbreeding?

Female flowers grow above male flowers, which keeps pollen from falling down on stigmata of the same plant. The plants release pollen before stigmata fully mature. BAD POLLINATION TIMING Self-incompatibility genes prevent an individual from mating with itself. POSITION, TIMING, INCOMPAT GENES NOT The plants produce many more female flowers than male gametes to ensure some amount of cross-fertilization. Male and female gametes produced by the same plant have different numbers of chromosomes. Self-fertilization, or inbreeding, causes reduced fitness because, without sexual reproduction between different genotypes, harmful recessive alleles tend to accumulate. A self-fertilizing plant that has a single recessive allele for a harmful condition is more likely to produce affected offspring than a plant that out-crosses with an unrelated mate lacking the allele. Natural selection favors the evolution of mechanisms that prevent male and female gametes of the same individual from combining. Anthers release pollen, the male gamete. Stigmata are the part of the female flower structures that receive pollen and facilitate germination. Monoecious plants produce both male and female flowers, whereas hermaphrodites make one type of flower that contains male and female gametes. One strategy both monoecious and hermaphroditic plants evolved to avoid inbreeding is releasing pollen before female flower structures fully develop. If the stigmata are not receptive to the pollen when it is released, fertilization cannot take place in the female flower structure. Some monoecious plants also avoid self-fertilization by growing female flowers above male structures. Pollen is unlikely to fall on female flowers if the stigmata are higher than the anthers. Like all plants, monoecious plants produce more pollen than they produce stigmata in flowers since pollen disperses widely. Both monoecious and hermaphroditic plants have evolved self-incompatibility genes that prevent a plant from forming viable offspring using its own pollen. Dioecious plants do not have self-incompatibility genes since a single plant has either male or female reproductive organs, not both. No plants avoid inbreeding by having male and female gametes with different numbers of chromosomes. Their gametes must be able to fertilize gametes from other individuals of their species that have the same number of chromosomes

One of the challenges for individuals that have both male and female functions is the problem of, ALTERNATIVE TO THIS PROB CAN OUTCROSSERS BE HERMAPHS?

GAMETS ON SAME FLOWER SELF FERTILIZE, self-fertilization, inbreeding depression OUTCROSSING ALTERNATIVE-->CAN BE HERMAPHS WHO SEQUENTIALLY ENABLE THEIR SEX FUNCTIONS a fish species common in coral reefs, can be functionally female when it is a small adult but then becomes functionally male later in life when it has grown larger Other species have self-incompatibility genes. Individuals with the same self-incompatibility genotype—including an individual mating with itself—cannot produce offspring. the self-fertilizing individuals can benefit by avoiding the cost of meiosi

Classify the descriptions of mating strategies as promiscuity, polygyny, polyandry, or monogamy.

GENETIC SUPERIOR SPERM OR BENEFITS FROM MULT MATINGS--POLYANDRY POLYANDRY-->SING FEMALE MULT MALES (OPPOSITE POLYGYNY) MALE DEFENDS FEMALE GORUP OR RESOURCES FEMALE NEEDS-->POLYGYNY NO SOCIAL BONDS WITH MULTIPLE PARTNERS MONOGAMY-->PERSISTING BOND BW TWO HWEN BOTH MAKE SIGNIF CONTRIB TO OFFSPRING SURVVIAL Mating strategies are the social connections between the sexes that evolved to increase fitness. At one extreme is promiscuity, in which both sexes mate with multiple partners and do not form social connections with any of the partners. At the other extreme is monogamy, or pair formation, which lasts at least as long as it takes to raise offspring. Although many monogamous pairings involve extra-pair copulations, it is the social bond between two adults that defines the monogamous relationship. Monogamy occurs when males and females both make significant contributions to the survival of their offspring. Between the extremes of promiscuity and monogamy are two polygamous strategies, polygyny and polyandry. In the animal world, polygyny is the more common of the two. It occurs when males compete for coveted resources and protect groups of females, thereby gaining mating rights to multiple females. Conversely, polyandry is the strategy in which the female is the more promiscuous sex, while the males mate with only one female. Polyandry usually occurs when females are seeking to birth genetically diverse offspring or when females receive tangible benefits from each male with whom they mate.

GOOD GENES HYPOTH, HOW DIF FROM OTHER HYPOTH

GENOTYPE, WHILE , known as the good health hypothesis, individuals choose the HEA;THIEST mates. Good health could be the outcome of either superior genetics OR a superior upbringing with abundant RESOURCES NOT ALWYAS GENETICS As a result, the good genes hypothesis and the good health hypothesis are not mutually exclusive. Females might prefer healthy males because such males may be both genetically superior and pose a lower risk of passing on a number of different parasites and diseases. ENVIRO CONDS COULD MAKE THEM HEALTHY

Which statement about pathogen-host evolution is FALSE?

Most host species have much longer generation times and much smaller population sizes than the pathogens that infect them.-->TRUE Hosts tend to evolve at slower rates than pathogens, so hosts are often unable to evolve ways to counteract the effects of pathogens. This is true. Pathogens tend to have shorter generation times than hosts, which enable them to evolve faster.' The greater range of genetic combinations produced by sexual reproduction may make hosts better suited at combating pathogens. When species have variations in both types and abundance of pathogens, asexual reproduction provides an evolutionary benefit.

Plants have several ways in which the sexual structures are arranged, which affects their mating strategies, Flowers that have both male and female parts within each flower are known as ? flowers., WHICH ARE HERMAPHRODITES

PERFECT FLOWERS Plants that have separate male and female flowers on the SAME individual PLANT are known as monoecious, HAZELNUT When an individual plant contains ONLY MALE flowers or ONLY FEMALE flowers, the species is known as dioecious. white campion By definition, plants that are hermaphrodites are also monoecious: male and female flower organs are, after all, on the same plant. and unisexual individuals (dioecious) have evolved from hermaphroditic ancestors many times Populations of some plant species can be composed of a complex mixture of hermaphrodites)PERFECT), males, females (DIOECIOUS), and monoecious individuals. In other species, individual plants produce both perfect flowers and flowers that are only male or only female.-->ONE SPP, MULTIPLE ARRANGEMENTS Hermaphroditic plants, such as the St.-John's-wort wildflower, possess perfect flowers that contain male and female structures within a single flower ONLY PERFECT NOT MONOECIOSU, MUST BE SAME FLOWER

One result of sexual selection is sexual dimorphism, which is a difference in the ? between males and females of the same species. Sexual dimorphism is seen in honeybees and sockeye salmon, which we discussed earlier in this chapter. Sexual dimorphism includes differences in body size, ornaments, color, and courtship behavior. 2 layers dimorph; EXAMPLE OF DIMORPH IN BODY SIZ

PHENOTYPE differences in: body size, ornaments, color, courtship behavior. related to fertilization—such as GONADS—are referred to as primary sexual characteristics, while traits related to differences in; body SIZE, ORNAMENTS, COLOR, and COURTSHIP are known as secondary sexual characteristics. used to display sexuality? health to breed?\ s because there has been selection for an increased number of gametes produced or for an increase in parental care by ONE sex. In fish and spiders, for instance, egg production is directly related to body size. \In this case, selection will favor the evolution of traits that help males compete, such as weapons for combat. Such weapons include the antlers of male elk, COMPETITION LARGER APPENDAGE/BODY SZIE FEMALES CAUSE THIS female, is particularly choosy when selecting a mating partner. In these cases, female selection of males with particular traits can cause the sexual selection for those traits, such as male deer growing antlers. Over the 37-year period, the rate of horn growth declined by 12 percent in the region of high-hunting pressure but showed no change in the region of low-hunting pressure. In short, increased hunting caused artificial selection for smaller horn size.-->SEX DIMORPH hunters either prefer or are required to harvest only the largest males-->STONE'S SHEEP

Identify the conditions that favor self‑fertilization over outcrossing in a hermaphroditic plant species.

Pollinators are required for many plants to sexually reproduce. Genetic diversity can help some species survive in rapidly changing environments.-->RAP CLIM CHANGE FAVOR OUTCROSSING small population size high herbivore activity A small population size also favors self‑fertilization over outcrossing. Outcrossing requires the joining of male and female gametes from different individuals. If other individuals are scarce, a hermaphroditic plant may undergo self‑fertilization to reproduce.-->SMALL=TROUBLE FINDING MATE In contrast, high pollinator activity favors outcrossing because pollinators carry the male gamete from one plant to the female gamete of another plant for fertilization. Rapid climate change also favors outcrossing because a genetically diverse population is more likely to contain individuals that can survive in a new environment.

? is a mating system in which a single individual of one sex forms long-term social bonds and mates with more than one individual of the opposite sex. ? MORE COMMON THAN?

Polygamy Most often, a male mates with more than one female, which is known as POLYGYNY For example, the largest and healthiest male elk will travel in a herd of females and mate with them. Polygyny also can occur when a male is able to defend a group In some species, polygyny evolves when males compete for females and the females all prefer only the few best males. when a male can control access to a resource that is attractive to multiple females LESS MALES SO COMPETE FOR FEMALE SHOW THEY STRONG. When a male guanaco PATAGONIA CAMEL defends a wetland from other males, he is able to mate with the females who come to eat the plants occasional wetlands that grow high-quality vegetation.

PROMIISCUITY DIF FROM OTHER MATING SYSTEMS?

Promiscuity is a mating system in which individuals mate with multiple partners and do NOT LASTING SOCIAL create a lasting social bond, MOST COMMON BC EASIEST? Promiscuity is universal among outcrossing plants because they send pollen out to fertilize the eggs of multiple individuals and receive pollen from multiple individuals. MULTIPLE OF EACH MATE Whether a particular sperm is the first to find an egg is largely a matter of chance, although males that produce the most sperm or pollen and males that produce the most competitive sperm or pollen are bound to father the most offspring

The _____ hypothesis states that sexual reproduction allows hosts to evolve fast enough to counter the rapid evolution of parasites. The Red Queen hypothesis only applies to organisms that reproduce _____.

Red Queen, sexually

If sexually selected TRAITS indicate intrinsic attributes of male quality—at least initially, before runaway sexual selection occurs—we are then faced with a paradox. Presumably, extreme traits burden males by requiring ENERGY and RESOURCES to maintain them, and they make males more conspicuous to PREDATORS. BUT If a male can survive with sexual traits that require extra energy to build or that increase the risk of predation, these traits might signal a ? genotype. DO THEY USUALLY OFFSET THIS HANDICAP? WHAT SORTS OF THINGS CAN THESE SEX TRAITS/HANDICAP APPLY TO

SURVVING W HANDICAP=superior . This idea, known as the handicap principle, argues that the greater the HANDICAP an individual carries in terms of a more extreme trait, the greater its ability to OFFSET that handicap with other superior qualities. and showy plumage might communicate to females that because he has the energy to build elaborate feathers, he can RESISTS PARASITES and pathogens->If this resistance can be inherited by the offspring of the males, then the secondary sex characteristics are honest signals of the genetic superiorit HONEST SUPERIORITY SECOND SEX CHARS expressing attractive traits while being exposed to parasites and pathogens may indicate genetic superiority. MIGHT CHOOSEINFECTED INDIV females prefer louse-free males to louse-infested males by a ratio of three to one. females prefer males with longer spurs on their lower legs. Longer spurs are linked genetically to major histocompatibility complex (MHC) genes that influence susceptibility to disease. Males with longer spurs have MHC alleles that are linked to longer life spans.

For most species of turtles, embryos that incubate at lower temperatures typically produce males, whereas those that incubate at higher temperatures produce females. Higher temperatures from global climate change could lead to skewed sex ratios among offspring and a reduction in breeding success as males become fewer in number. What behaviors during the egg‑laying season might lead to potential behavioral adaptations that could help maintain an even sex ratio? TEMP DEPENDNET ENVIRO SEX SELECTION

Sea turtles that nest during the cooler part of egg‑laying season. COOLER SZN PART At least one additional behavioral adaptation might help to maintain an even sex ratio. Turtles that clutch multiple times have the opportunity for clutches to incubate at different temperatures. AND Pond turtles that nest in more SHADED areas around their ponds. Pond turtles that have multiple clutches throughout egg‑laying season. MULTIPLE CLUTCHES

CHANGING FIG WASP SEX RATIO , WHAT KIND OF COMP FIG WASPS HAVE BASED ON SEX RATIO?, EFFECT WHO'S FITNESS

Similar to the bees that we discussed at the beginning of this chapter, wasps can easily adjust the sex ratio of their offspring because fertilized eggs become daughter The larvae metamorphose into adult wasps and breed with their siblings while still inside the flower. The young males breed with the young females, chew a hole in the side of the flower, and then die. The fertilized young females then escape through the hole and fly off to pollinate a new fig flower. because male competition for females is among brothers. This phenomenon, known as local mate competition, occurs when competition for mates takes place in a limited area and only a few males are required to fertilize multiple females. AND ONE MALE FERTS MANY DAUGHTERS When only one fertilized mother enters a fig flower, the only males available to fertilize her daughters are her sons. From the mother's perspective, it does not matter which son passes along her genes to her grandoffspring. One son can fertilize multiple daughters, which means there is no fitness benefit to producing many sons. so it is in the mother's best interest to produce many daughters SO mothers that produce a higher proportion of daughters than sons will have more grandoffspring and therefore greater evolutionary fitness. Local mate competition When competition for mates occurs in a very limited area (SOMETIMES OWN SIBLINGS MATE)and only a few males are required to fertilize all the females. EFFECT MOM'S FITNESS-->one son can breed with multiple daughters in an isolated population, EFFECT GRANDOFFSPRING Sometimes, however, two or more females lay their eggs in the same flower. In this situation, a mother's male offspring can mate either with their sisters or with the daughters of the other mothers. When this occurs, a mother will obtain greater fitness if she produces extra sons so that she has enough sons to fertilize all the females in the flower. EXTRA SONS SO NOT JUST SIBLINGS the mothers lay a higher proportion of male eggs.

asexual for generations, probs if little harm of ? good type of enviro for asexual

Similarly, some groups of protists have existed for hundreds of millions of years and appear to lack sexual reproduction. One way that such species could avoid extinction is by producing offspring more rapidly than new deleterious mutations could arise. MUTATION some individuals would always retain the nonmutated parental genotype and produce the next generation, a process known as clonal selection. If the environment were homogeneous across time and space, parents that are well adapted to the environment could use asexual reproduction to produce clonal offspring that are also well adapted Temporal and spatial variation in the biotic environment—particularly variation in the occurrence of different pathogens—could provide a large advantage to the genetic variation created by sexual reproduction. offspring are likely to encounter different environmental conditions than their parents did.

A sexually mature diploid female with 20 chromosomes in each cell is ready to reproduce via parthenogenesis. One of her germ cells begin meiosis and proceeds through the first meiotic cell division. However, meiosis then stops, and the cells produced during the first meiotic division become embryos from which new individuals arise with NO fertilization from a male. This meiotic event involving a single germ cell will produce _____offspring, each with _____ chromosomes.

TWO WITH 20 CHROMS EACH-->THEY'RE DIPLOID

Parthenogenesis can produce offspring that are clones of the parent when germ cells _____.

The correct answer is not pass through the first meiotic division, but not the second meiotic division Genetic recombination and independent assortment are part of the first meiotic division (1ST PART HALF CLONE PROCESS) undergo fusion of haploid cells to develop into diploid embryos-->SECOND PART HALF CLONE PROCESS WOULND'T BE CLONES develop into egg cells without going through meiosis

natural selection will favor any parents that produce offspring of the less abundant sex. he best sex ratio strategy for parents depends on the frequencies of males and females in a population ALREADY

The evolution of the sex ratio is said to be the product of frequency-dependent selection, which occurs when natural selection favors the rarer phenotype in a population. When researchers examined the sex ratios among the different sockeye salmon populations, they found that the populations ranged from 36 to 47 percent males due to the long-term effects of fishing, those with much larger males than females are experiencing declines in the ratios of males to females due to fishing regulations that require harvesting the largest fish SALMON MALE LARGER PHENOTYPE ARTIF SELECTED FOR

A diploid female that reproduces via parthenogenesis possesses germ cells that undergo complete meiosis. Choose the answer that explains how her gametes form a diploid embryo.

The gametes that result from complete meiosis are NOT already diploid. The haploid gametes fuse to form a diploid cell. NOT FERTILIZIED IN PARTH

In most species containing individuals that are either male or female, the proportion of males and females changes over time. The table shows sex ratios in a wasp species over a 10-year period. Wolbachia is a bacterium that infects the cells of many insects and other invertebrate species. A key feature of the biology of Wolbachia is that it is transmitted only through the eggs of infected females. Therefore, it gets no benefit from infecting males. In many species of invertebrates, Wolbachia has evolved different ways to discount or eliminate the contribution of males to the next generation. Complete the passage that describes how the ratio of males and females might change if the wasps became infected by the Wolbachia bacteria.

The inability of the male offspring of infected females to fertilize the eggs of uninfected females does not give a fitness disadvantage to infected females. Producing females increases lifetime reproductive outpu The key to understanding the effect of the bacterium Wolbachia on sex ratios of infected wasps is that transmission from one generation to the next is only through females. Wolbachia cannot be transmitted to another generation through males or through uninfected females. In order to maximize its transmission to the next generation, Wolbachia has evolved to affect the reproductive strategies of its host to favor its transmission. Since an infection in males eliminates the possibility of transmission and is a dead‑end for the bacterium, Wolbachia gets no fitness benefit from infection of males. In causing sperm to be unable to fertilize eggs of uninfected females, who cannot become infected by infected males, a dead end pathway to Wolbachia transmission is eliminated. Male elimination is also produced by manipulating meiosis in eggs to produce diploid eggs, which in wasps become female. This is one type of parthenogenesis. In such populations, the sex ratio is female skewed. In a population of wasps infected by Wolbachia, male offspring of infected females are unable to fertilize eggs of uninfected females. This gives a fitness advantage to infected females CAN BE FERTILIZED. In OTHER cases, OF PARTHENOGENESIS the chromosome complement of infected eggs replicates, producing diploid eggs, which are females in wasps. This parthenogenesis eliminates males. The bacterium can spread rapidly because the reproductive output of infected females and the survival rate of their offspring is increased. In a short period of time, sex ratios can become highly female biased.

In most species containing individuals that are either male or female, the proportion of males and females changes over time. The table below shows sex ratios in a wasp species over a 10-year period. Select the graph that correctly shows the proportion of male and female wasps commonly found in a population over a 10-year period.

The proportion of males and females in a population changes from one generation to the next due to chance events and environmental conditions. Once one sex becomes more common or more rare than the other, natural selection may favor parents that produce more of one sex over the other. In this dataset, females are the more common sex in years 1 and 2, but become the less common sex in years 3, 4, and 5.Females again become the more common sex in years 6 and 7. This is a result of frequency‑dependent selection, which favors the rare sex and causes the sex ratio to equilibrate around one‑to‑one. When females are more common, a female that produces more sons will have greater fitness than one that produces more females or an even number of males and females. When females are common, some may not find mates. Parents that produce sons will have higher fitness, and the proportion of males in the population will tend to increase. Frequency‑dependent selection will operate in the same way when males are more common.

Testing the Red Queen Hypothesis

The snails can become infected by parasites, including TREMATODE worms in the genus Microphallus. In this system, the Red Queen hypothesis is that the sexual reproduction of the snails allows them to evolve adaptations against the parasite RAPIDLY enough to persist. These eggs exit the duck when it defecates in the water, thereby completing the cycle. Not surprisingly, Microphallus is most abundant in shallow waters of lakes where ducks feed. life begins when the snails inadvertently ingest worm eggs arvae that form cysts in the snail gonads, causing the snails to become sterile. STERILIE SNAIL Ducks then eat the infected snails, and the pathogens mature sexually inside the intestines of the ducks, where they produce eggs asexually. IN DUCK INTESTINE These eggs exit the duck when it defecates in the water, thereby completing the cycle In short, there is an evolutionary race between hosts, which are trying to evolve adaptations rapidly enough to combat the pathogen, and pathogens, which are trying to evolve adaptations rapidly enough to breach host defenses. The hypothesis that sexual reproduction allows hosts to evolve at a rate sufficient to counter the rapid evolution of parasites is called the Red Queen hypothesis, rapid enough=population persists that was causing widespread amphibian deaths. The pathogen is a type of chytrid fungus-->dozens amphibious extinctions, As we have seen, sexual reproduction produces offspring with a greater range of genetic combinations, some of which might be better suited to combat the pathogen. even if faster pathogen evolution

If sexual reproduction is so costly, then it must persist because it provides substantial benefits. These benefits include PURGING/DEALING W PATHOGEN AND PARASITES

These benefits include purging harmful mutations and creating genetic variation that helps offspring deal with future environmental variation, including the existence of rapidly evolving parasites and pathogens. mutations are transmitted from one generation to the next, so they accumulate over generations, especially if the asexual parents produce clonal offspring. random assortment of genes during meiosis in sexually reproducing organisms, deleterious mutations may not be transmitted to gametes WILL NOT BE IN EACH GAMETE BC GAMETES NOT JUST COPIES OF EACH OTHER , ALL SAME GENOTYPS gametes that are produced, the SUBSET that forms ZYGOTES may not contain the mutation An offspring that is homozygous for the harmful mutation is likely not viable and will fail to breed and pass the mutation to the next generation. In short, sexual reproduction can help purge mutations through multiple mechanisms.

ASEXUAL reproduction is favored when the sex ratio of a population is heavily skewed because Asexual reproduction is also favored in small population When food is abundant and no other threats exist, a species may benefit from reproducing asexually

an individual can reproduce even when it cannot find a mate of the opposite sex where finding a mate is difficult. I. to grow the population as quickly as possible while conditions are favorable.

Because females are ?, males should compete strongly with other males for the opportunity to breed. This intense competition among males for mates has resulted in the evolution of male traits that are either used to attract females or used in contests and combat among males. results in Natural selection for sex-specific traits related to reproduction is referred to as ?

choosy, stronger male competition (repro success more variable) result=sexual selection attracting or fighting related to sexual selec

COST OF MEIOSIS: LESS ENERGY BUT HOW IS IT A COST

each parent contributes only one set of chromosomes to each offspring sexual reproduction has an additional impact on fitness: the cost of meiosis. Females using either mode of reproduction produce the same number of offspring, but the female parent using sexual reproduction leaves behind half as many copies of its genes as a female using asexual reproduction. 2 SET CHROM IN ASEX REPRO

In some species, sex is determined largely by the environment, in a process known as ? temperature-dependent sex determination (TYPE OF ENVIRO SEX DETERMINATIONO) is a type of ? ?., TEST SPP FOR THIS, HWY COULD IT WORK TO SHOW ADAPTIVENESS OF SEXES AT DIF TEMP

environmental sex determination including several species of turtles, lizards, and alligators, the sex of an individual is determined by the temperature at which the egg develops. turtles, embryos incubated at lower temperatures typically produce males, The reverse is generally true in alligators and lizards. LOWER TEMP FEMALES? PHENOTYPIC PLASTICITY eggs laid deeper in the nest experience cooler temperature and are more likely to hatch as males LOGGERHEAD TURTLE if the temperatures that cause eggs to become males also produce males that experience higher fitness ONLY ONE WHERE FEMALE JAKCKY DRAG SAW FEMALE HATCHING AT DIF TEMPS females are produced when incubated at low and high temperatures, whereas both males and females are produced when incubated at intermediate temperatures. HORMONES TO PRODUCE MALES ALL TEMPS TOO At the end of 3 years, the researchers determined the number of offspring produced by adults that had been incubated as eggs at different temperatures. males incubated at the intermediate temperature subsequently fathered more offspring than males incubated at the low and high temperatures. t temperature-dependent sex determination appeared to be adaptive. FEMALES GAVE SAME NUM EGGSANY TEMP warmer temperatures have the potential to alter the sex ratios of species such as turtles and alligators. In species that produce more females under warmer temperatures, such as sea turtles, researchers in 2017 predicted that populations would not be negatively affected since one male can fertilize several females. males under warmer conditions, it is more likely that we would observe population declines ASSUMING NO BEHAVIOR CHANGES

Researchers have discovered that artificial selection pressure caused by human fishing activities can skew sex ratios in salmon populations. This is due to the fact that larger fish are preferentially harvested and male salmon are typically larger than female salmon. This means that males are inadvertently harvested more often than females. Choose the other salmon traits that might evolve in response to intense fishing practices that selectively harvest larger adult fish.

faster development to maturity Salmon grow rapidly until they reach sexual maturity between two and eight years of age. Fish that mature later develop larger body sizes than fish that mature at younger ages. Large fish have genes for bigger body sizes and delayed development to sexual maturity. Removing large fish from the population means they cannot contribute their genes to the next generation. Only the small fish that mature earlier survive to spawn the next season. Thus, artificial selection caused by fishing favors fish with smaller bodies that become sexually mature earlier in development. FASTER DEVELOP MEANS SMALLER FISH, NOT LARGER IN SMALLER TIME Intense selective fishing is unlikely to affect body color or pathogen resistance, as these traits do not affect the likelihood of being caught in the fishers' nets and removed from the population. Salmon may evolve darker body color as camouflage to prevent predation by birds. They may evolve stronger pathogen resistance in response to a disease outbreak. However, these traits are unrelated to artificial selection imposed by fishing practices.

In a population of snails occupying a single small pond, some individuals possess a single sex and some individuals are simultaneous hermaphrodites that are capable of reproducing with both males and females. After monitoring the snail population for several years, you find that an average male-only pond snail produces 60 offspring per week during the peak of the reproductive season, while an average female-only pond snail produces 40 offspring per week during the same period. In addition, the average hermaphroditic pond snail produces 30 offspring using its male function and 20 offspring using its female function per week. What is the order of these three reproductive strategies, from lowest to highest, in terms of their relative fitness?

female < hermaphrodite < male

RESULT OF MONOGAMY

from mate guarding , While human patterns are distinct from genetic monogamy, defined as two individuals who only reproduce with one another, levels of extra pair Monogamy occurs in about 90 percent of bird species because male birds can offer much of the same care to offspring as females, such as incubating eggs, gathering food for the chicks, and protecting the chicks from predators particularly because females lactate, and the growth and survival of mammal offspring are thus less reliant on a male's presence.

In species where the males have two different types of sex chromosomes, as in mammals, researchers have found that the females of some species can control whether X-chromosome or Y-chromosome sperm are allowed to ? their eggs. WHAT COUDL MOM RED DEER DO TO FETUS BASED ON TIME OF YEAR?

fertilize, CHOSE SEX CHROM SPERM TO FERTILIZE THEM BIRDS WHERE FEMALES HAVE TWO DIF CHROMS FOR SEX females of some species can determine the sex ratio of their offspring by controlling the fraction of their eggs that receive the Z versus the W chromosome during meiosis All of this suggests that females can have a large influence on the sex ratio of her offspring at the time of fertilization. OR CHOOSE NOT TO FERTILIZE EGG insects—bees, wasps, and ants—the female determines the sex of her offspring by whether or not she fertilizes the egg different approach to controlling the sex ratio of offspring is through selective abortion. In red deer (Cervus elaphus), for example, adult females breed in early autumn and give birth the following spring. harvested red deer to determine whether the sex ratio of the fetuses was affected by the mother's age—-->RED DEER NEED MILK yearling mothers, which are smaller and have less energy, were much more likely to produce the less energetically expensive daughters yearling mothers carried about 25 percent male fetuses and 75 percent female fetuses SEX RATIO CHANGED EVEN IN GESTATION They found that the yearling mothers initially had a nearly even sex ratio of offspring. As winter progressed, however, the proportion of male fetuses declined sharply, suggesting that the yearling mothers were capable of selectively aborting the more expensive male fetuses as gestation progressed selectively aborting MALE FETUS IN WINTER, STARTING W EVEN RATIO ALMOST ALL FEMALE BY FEBRUARY we can compare the conditions that favor a one-to-one sex ratio with the conditions that favor a deviation from that ratio. OTHER CASES SELECTION NOT FAVORING ONE TO ONE SEX RATIO Let's imagine, for instance, that a population has more females than males and each male breeds with only one female. In this situation, some females would remain unbred. A parent that produces all sons would have higher fitness than a parent that produces an even number of sons and daughters, because some of the daughters might not find mates. GETTING ONE SEX TO BE ALL BRED-->FEMALES a parent that produces all daughters would have higher fitness than a parent that produces an even number of sons and daughters, because some of the sons might not find mates-->MALE SURPLUS As you can see in this example, individuals of the LESS abundant sex enjoy greater reproductive SUCCESS because they compete with fewer individuals of the same sex for breeding.>>SAME SEX COMP FOR MATE

special bird genetics , who does Extra-pair copulations surely help? extra-pair copulations has selected for?, a behavior in which one partner prevents the other partner from participating in extra-pair copulations.

form a single social bond with a male partner, DNA analysis of offspring in a nest has revealed that the offspring often have different fathers. has a social bond by spending most of her time with only one male, she is actually breeding with other males, a behavior known as extra-pair copulation., 90% thot monogamous males outside nest fathering more eggs than just those in his nest, but how does this behavior increase the fitness of a female? One way would be if her reproductive success is improved by creating greater genetic variation among her offspring so at least one of her offspring might be better suited to future environmental conditions. She could also benefit if the neighboring males have superior genes than her mate. . As you can see in Figure 8.20, the amount of swelling in the wing was greater in offspring produced by extra-pair copulations, which demonstrates that they had a stronger immune response-->In a bird known as the bluethroat obtain superior genotypes from another male and produce offspring that have superior immune systems. select for mate guarding individual simply stays near its mate and keeps other potential suitors away. For example, a species known as the burying beetl OFFPSRING COMPETITION The male often tries to attract additional females by releasing an attractive smell, but the original female attacks the male so he cannot attract additional females, whose offspring would compete with her own. the male's heart stops and he dies with his appendages still stuck inside the female, making it impossible for the female to mate again. SPERM-TRANSFERING APPEND OF ORB-WEAVER

Some species of freshwater snails can reproduce both sexually and asexually, but asexual reproduction yields more offspring. Identify the condition that favors sexual reproduction.

high parasite abundance abundant food supply small population size heavily skewed sex ratio Sexual reproduction between two individuals requires a greater energy investment because of the process of finding a mate, but it produces more genetic variation among offspring than asexual reproduction. Asexual reproduction does not require a mate and may produce a greater number of total offspring than sexual reproduction, but these offspring are often nearly identical to one another. Because these two modes of reproduction have different consequences, various environmental conditions may favor one breeding strategy over the other in species that can reproduce both sexually and asexually. For example, some species of freshwater snails employ a mixed breeding strategy, meaning they can reproduce either sexually or asexually, depending on the circumstances. This allows the snails to increase their overall fitness in different environments that favor different breeding strategies. Although asexual reproduction typically produces more offspring, a species may benefit from sexual reproduction when parasites are highly abundant. Sexually reproducing snails that are parasite-susceptible have a greater chance of producing some parasite‑resistant offspring because of genetic variation. Asexually reproducing snails that are parasite-susceptible produce only genetically similar offspring. ASEXUAL reproduction is favored when the sex ratio of a population is heavily skewed because an individual can reproduce even when it cannot find a mate of the opposite sex. Asexual reproduction is also favored in small populations where finding a mate is difficult. In both cases, asexual reproduction may allow the population to grow more quickly than with sexual reproduction. Because asexual reproduction occurs without a mate, it often requires less time and energy. When food is abundant and no other threats exist, a species may benefit from reproducing asexually to grow the population as quickly as possible while conditions are favorable.

FEMALE CHOICE CONTINUED INFLUENCE , continue to evolve trait needs?

if females prefer longer tails in their mates and there is genetic variation to select from, longer tails will continue to evolve in males. When selection for PREFERENCE of a sexual trait and selection FOR THAT TRAIT continue to REINFORCE each other, the result can be runaway sexual selection. needs gen variation in male pop, 2 selection forces other large male ornaments such as horns, tusks, and antlers. Runaway selection continues until males run out of genetic variation for the trait or until the fitness costs of possessing extreme traits begin to outweigh the reproductive benefits.

Cost of meiosis

loss gen divers using sex repro y asexual reproduction inherit DNA from a single parent. This can be accomplished through either vegetative reproduction or parthenogenesis hermaphrodite repro when not a plant? or separated plants that cannot self fertilize->A hermaphrodite can pass on eight copies of its genes by producing four eggs that are fertilized by another individual's sperm (female function?) and four copies of its genes when it uses its sperm to fertilize another individual's eggs.

some organisms reproduce asexually by producing an embryo without fertilization, a process known as ?. In most cases, parthenogenetically produced offspring arise from diploid eggs, which do not require any genetic contribution from sperm. Animal species that reproduce only by parthenogenesis are typically composed entirely of ?. CLONING VS PARTHOGENESIS , BOTH USE WHAT In contrast, genetically variable offspring are produced when germ cells proceed ? or ? through meiosis.

parthenogenesis PLANTS, INVERTS FEMALES lizards, amphibians, birds, and fishes., OFFSPRING GEN IDENT TO MOTHER, SO STILL USE GAMETES/SEX TISSUE UNLIKE VEG REPRO isolated female boa constrictor gave birth to two litters of daughters through parthenogenesis-->The recessive caramel coloration of the mother was passed on to all her clonal daughters that many species can reproduce through both sexual and asexual reproduction. LIKE SNAKES Parthenogenesis CAN BE produce offspring that are either CLONES of the parent or offspring that are genetically VARIABLE (MEANING MEIOSIS WITH THIS RECOMBINATION OF STUFF) Clones are produced when GERM cells develop directly into egg cells without going through WITHOUT MEIOSIS partially (ONLY first meiotic division) OR ENTIRE MEIOSIS, SO DIPLOID -->Although a sexual union is not involved, these eggs differ from one another genetically because of recombination, and the independent assortment of chromosomes during the first meiotic division

Parthenogenesis can produce offspring that are genetically variable when germ cells _____.

pass through at least one stage of meiotic division

we expect natural selection to favor the reproductive strategy(THUS FLOWER ARRANGEMENT) with the highest fitness. TCOMPARONG WHAT TO SEE TRADEOFF, FITNESS MEASURED IN HERMAPH FROM COMBO MALE/FEMALE FUNCTION BOTH FUNCTIONS the total fitness achieved from being a hermaphrodite (i.e., fitness through male function plus female function) exceeds the fitness of being ONLY a male or only a female. WHICH FLOWERS EASIER FOR HERMAPHRODITES WHY WOULD OTHER ORGS HAVE HARDER TIME BEING HERMAPH hermaphroditism should occur commonly among sedentary ? animals that mate by simply shedding their gametes into the wate

separate versus combined sexual function. For instance, in organisms such as flowering plants, a plant could evolve to make male flowers, female flowers, or hermaphrodite flowers we need to compare the amount of fitness an individual would gain by investing in only male or female reproduction only giving up a small amount of male fitness, then selection will favor the evolution of hermaphrodites-->AKA MORE EGGS AND STILL LIL SPERM REDUCTION? In the case of flowers that reproduce with the assistance of pollinators, the basic flower structure and the floral display necessary to attract pollinators are already in place in male flowers and female flowers. This should make the fitness costs of adding a second sexual function relatively small while providing large fitness benefits. two-thirds of all flowering plant species have evolved to be hermaphrodites. In this example, the fitness of a hermaphrodite equals the fitness derived from male function (HM) plus the fitness derived from female function (HF). HM AND HF ARE RESPECTIVE SEX FUNCTIONS OPPOSITE: but the total fitness OF COMBINED FUNCTIONS is less than males and females would experience if they were to retain a single sexual function. being male requires large expenditures of time and energy for attracting mates and fighting with other males COMPETITION AND NEERGY while being female requires specializations for egg production or time and energy needed to care for offspring DIF COSTS FOR EACH SEX FUNCITON Because these costs can be quite high, we would predict that hermaphroditism should occur rarely among animal species that actively seek mates and engage in brood care. SEDEN AQUATIC ANIMALS individuals add the other sexual function and experience a large decline in ORIGINAL sexual function

In mammals, birds, and many other organisms, sex is determined by inheritance of chromosomes. In both cases, the sex that has two different chromosomes—male mammals and female birds—produces an approximately equal number of gametes containing each sex chromosome. WHAT ELSE SEX CAN B FROM (SELF FERTILIIZTON OR NUMBER CHROMS)

sex-specific Birds have the opposite pattern of genetic sex determination: Males have two copies of the Z chromosome, whereas females have one Z chromosome and one W chromosome. BIRD Z W CHROMS AND FLIPPED sex that has two different SEX DETERMININD. chromosomes EQUAL OF EACH SEX, DETERMINES In honeybees and other members of their order (i.e., bees, ants, and wasps), sex is determined by whether or not an egg is fertilized. Fertilized eggs, which receive two sets of chromosomes, become females SEX W (NUMBER CHROMS NOT DIF ALLELES OF THESE--INSECTS In grasshoppers and crickets, for instance, all individuals are diploid, but females have two sex chromosomes, whereas males have only one.

sexual reproduction comes with a number of costs to the organism

sexual organs require considerable energy and use resources that could be devoted to other purposes. In addition, mating itself can be a substantial task. Many plants must produce floral displays to attract pollinators, and most animals conduct elaborate courtship rituals to attract RITUALAS GONADS FLORAL DIAPLSY ESP IN SHORTER MATING PERIOD FRENZY OF ENERGY TO THESE THINGS ENHANCING REPRO Such mating effort is not just energetically costly; it can also elevate the risk of herbivory, predation, and parasitism. mouse-size marsupials from Australia known as KALUTAS-->Combined with very high levels of testosterone, which suppresses the males' immune system, this frenzy of breeding activity ultimately kills all of the male

How does the Red Queen hypothesis explain a fitness benefit of sexual reproduction?

sexual selection allows hosts to evolve at a rate that counters the rapid evolution of parasites Sexual reproduction produces genetic variation that allows some offspring to survive evolving parasites. Hosts and harmful parasites are in a constant evolutionary competition. Parasites evolve to better infect the hosts, and hosts evolve to better avoid parasitic infection. Because parasites typically produce OFFPSRING MORE QUICKLY than their HOSTS, evolution can occur faster in the parasites, giving them an advantage in the race. The Red Queen hypothesis posits that sexually reproducing organisms compete with fast‑evolving parasites NOT AS FAST BUT BETTER GENETIC COMBOS, RESISSTANCE TRAITS by producing a wide range of genetic combinations in their offspring. If some of the offspring possess a genetic trait that resists parasite infection, then those individuals are more likely to survive long enough to reproduce, passing on that that trait to their offspring and into subsequent generations until the trait has spread throughout a population. Thus, sexual reproduction can allow populations of a host species to evolve resistance to parasites even as parasites are evolving to be better able to infect host species. Sexual reproduction minimizes the occurrence of recessive genetic disorders and often involves mate choice, but these features are not explained by the Red Queen hypothesis. The Red Queen hypothesis explains how sexually reproducing hosts maintain evolutionary rates fast enough to compete with quickly evolving parasite