Study Guide for Exam 2
Study Guide for Exam 2 BIOL 323
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This 5 page Study Guide was uploaded by Emma Marquez-Shaw on Tuesday October 11, 2016. The Study Guide belongs to BIOL 323 at California State University Chico taught by Rebecca Brunelli in Fall 2016. Since its upload, it has received 45 views.
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Date Created: 10/11/16
Study Guide: Exam 2 Anisogamy and Syngamy o Anisogamy: Sexual reproduction with unequal gamete sizes o Strategies: Male: Number of offspring Female: Parental investment o Syngamy: The fusion of two gametes in fertilization o Fun Sperm Facts: Sperm can live inside a woman up to 5 days Sperm can live outside up to 3 hours Human sperm size: 40 micrometer (4/100 mm) 280 milliliters of sperm per ejaculate Average speed of semen at the moment of ejaculation is 31 mph Human male ejaculates an average distance of 7 – 10 inches Average volume of semen per ejaculation is 1 teaspoon (more following abstinence) Each teaspoon can contain about 200 – 500 million sperm o Fun egg facts: Human egg is the largest cell in the body Takes about 47 days to travel down the fallopian tube Females are born with 2 million egg follicles Birth – puberty about 11,000 egg follicles die per month By puberty, only about 400,000 remain One per month released during ovulation (about 400 lifetime) Not many left by menopause Left and right ovaries randomly take turns 10 – 20 eggs mature each month, only one released Rest are absorbed o Twins Identical – 1 egg and 1 sperm Fraternal – 2 eggs and 2 sperm Semiidentical (rare) – 1 egg and 2 sperm o Sex Paradox Article Study eukaryotic organisms that have weird sex, or those that have no sex at all. o Potential Reproductive Rate (PRR) Males reproductive success depends on number of eggs he can fertilize Limited by the number of partners Additional mating = higher fitness Females reproductive success limited by number of eggs she can produce to bring to term Resources are important o Variance in Reproductive Success Some males have lots of offspring Some males have fewer offspring Most females have offspring Leads to male competition Asexual and Sexual Reproduction o Asexual (AR): Offspring are clones o Sexual (SR): Two parents combine genes to produce unique offspring o Asexual Reproduction Can go extinct due to being exact clones Species that use AR: Single – celled organisms Fungi Plants Some animals (whiptail lizards) o Disadvantages of SR / Advantages of AR Need 2 (male/female) to make one baby and only half can reproduce Every member can produce offspring Genome dilution: only give ½ of your genes to offspring 100% of your genes are passed on Meiosis takes time and energy Mitosis takes less energy Costs time and energy to find a mate No mates needed Risks: predation, injury, sexual cannibalism, STDs No risk from the preceding list Fewer individuals to survive disaster More individuals may survive in disasters o Disadvantages of Asexual Reproduction Genetic clones: mutation could devastate population No variation means low ability to adapt to a changing environment Population explosion can cause competition for resources o Benefits of Asexual Reproduction Rapid growth is important In stable environments Benefits only good for short term o Bdelloid Rotifers Only animal we have evidence for that has lasted millions of years Avoid going extinct in three ways Drying up Blowing away Lateral gene transfer o Four types of Asexual Reproduction Binary Fission Parent organism is replaced by two daughter organisms, because it divides in two Similar to mitosis, but BF involves simple cells Budding New individual grows off parent “Clone” Common in plants, fungi, sponges Fragmentation New individual grows from a fragment of parent Parthenogenesis (Virgin birth) Offspring develop from unfertilized eggs Only females (haploid) Sperm isn’t needed for eggs New Mexico Whiptail Lizard o No males exist Facilitative Parthenogenesis o Ability to switch between sexual reproduction and parthenogenesis o Example: Komodo dragon o Example: Aphids o Allows rapid population growth when conditions are favorable o Four Hypotheses Weismann’s Hypothesis Sex creates genetic diversity for natural selection to act upon Sex is important only in an unstable environment Fisher Muller Hypothesis Recombination speeds up adaptation o Brings advantageous mutations together faster Increases genetic variation Clonal interference: clones with beneficial mutations compete and interfere with each other’s growth Muller’s Ratchet Asexual species accumulates harmful mutations Drives asexual species extinct Sex helps escape harmful mutations Red Queen Hypothesis Coevolutionary arms race o Parasites/Pathogens evolve to live off of most common hosts o Hosts evolve to fight parasites/pathogens Sex maintains diversity to continue the fight Sex Determination o Autosome: any chromosome that is not a sex chromosome o Over 1,400 genes on an X chromosome o 70 – 200 genes on a Y chromosome o Homogametic Eggs All carry an X o Heterogametic Sperm ½ carry X, ½ carry Y o Types of sex determination XX or XY o Males determine sex o Mammals ZW/ZZ o Females determine sex o Birds, some reptiles, some fish, and crustaceans Haplodiploid o Fertilized egg = female o Unfertilized egg = male o Ants, bees, and wasps Temperature Determination o Warm = male o Cool = female o Most turtles, alligators, and crocodiles Environmental location o Green Spoonworm o Where it lands on the ocean floor determines sex Ways sex and gender have been categorized Anatomy Physiology Chromosomal makeup Genetic makeup Gender identity Gender role identity Gender role behavior o SRY Gene Sex Determining Region Y Located on the Y chromosome Responsible for determining sex o XInactivation One X chromosome in each cell is inactivated Barr body: inactive X chromosome Random, whether the paternal or maternal X chromosome is inactivated in each cell Once an X is inactivated, the daughter cells of that cell will always have the same X chromosome inactivated forever Female humans (and most mammals) are mosaics Happens at about a 20 cell embryo Sex Linked Traits o Always live on X chromosome o In some cases, can also be found on Y chromosome o Females gain two X chromosomes One from each parent o Males only gain one X chromosome One from the mother o Males are commonly exposed to X linked traits o Recessive and dominant alleles Different on X chromosomes than on autosomes Males have only one X X inactivation in females o Calico cats Always female (in normal development) X^O X^o
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