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Lecture 10

Lecture 10 (Ch.2 - Sex & Evolution).docx

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Ayesha Khan

NOTE: DUE TO POTENTIAL COPYRIGHT INFRINGEMENTS, THE SLIDES HAD BEEN TAKEN OUT BY OWNER. Lecture 10 (Ch.2: Sex and Evolution) SLIDE 1 SLIDE 2 - Focusing on other animals to understand our own SLIDE 3 - Father of theory of evolution - Stated that species evolve from other species through adaptation processes SLIDE 4 - Differences between individuals in populations - Variations in specific traits (height, colour, etc;) SLIDE 5 - These variations are heritable - Passed down from genetics from parent to offspring SLIDE 6 - Fitness passed on through their offsprings and spread around the population - These bright green frogs would blend into the trees so it’s difficult for other predators to see it and hence pass on the trait for bright greenness SLIDE 7 - If the traits are detrimental, then it won’t get pass on and eventually disappear - These dark green frogs are noticeable on bright green trees because they’re likely to be eaten and therefore not survive to pass on through successive generations SLIDE 8 - Survive long enough and reproduce successfully SLIDE 9 SLIDE 10 - These islands are home to several species of finches - Focus on ground finches - Banded 15K birds and noted their morphological characteristics - Also recorded environmental conditions and number of seeds of each plant species SLIDE 11 - Drought resulted in huge decline in the certain seeds that ground finches eat, especially small seeds which left the island with large hard seeds - Birds that survived were the larger birds with larger beaks because smaller birds can’t consume the remaining seeds - Larger size birds promoted the survival and small size was detrimental SLIDE 12 - Morphological features varies in the birds and the traits were heritable SLIDE 13 - Life evolved through process of natural selection - Huge diversity - Life can be diverse in many aspects; such as how reproduction occurs SLIDE 14 - Asexual: obtain all genetic material from one parent, so they’re identical - Mitosis: how single cell eukaryotes reproduce SLIDE 15 - Hydra: aquatic animal - Whiptail lizard: entirely female population; creating eggs through mitosis and don’t need to be fertilized by sperms SLIDE 16 - Not identical to parent - Two individuals come together and mix their genes and create a new individual - Fuse with each other and give each other the complement chromosomes NOTE: DUE TO POTENTIAL COPYRIGHT INFRINGEMENTS, THE SLIDES HAD BEEN TAKEN OUT BY OWNER. SLIDE 17 - Adaptive values to it SLIDE 18 - Helps to limit mutations - Random changes in the genome caused by DNA replication or exposure to chemicals - Many mutations are harmless while others are harmful - When it reproduces asexually, can’t get rid of harmful mutations because the genes are identical to parent; the mutations will continue to accumulate and it’s not good for survival SLIDE 19 - When you mix genes, the offspring has half of each parent’s genes; there are chances to weed out mutations SLIDE 20 - Eliminating harmful mutations - Creating beneficial gene mutations - For example, you have 4 kids and one of them eats a different type of food and therefore there’s less competition for resources (food) SLIDE 21 - ex. Two types of yeast, both types of yeast reproduce at the same rate during non-stressful environment SLIDE 22 - Added heat - Sexual reproduction allows for new combos of gene that allows the offsprings to grow in warm temperature - Asexual can’t come up with new genes so it just dies out eventually SLIDE 23 - Red Queen Hypothesis: SLIDE 24 - Continually upgrade defenses to parasites - The host has to continually evolve to keep out parasites because parasites can easily develop a key to get in SLIDE 25 - Males produce small mobile gametes call sperm - Females produce large immobile gametes call eggs SLIDE 26 - Reproduction requires investment from both parents: time and energy - Has to have enough nutrients to develop into a new organism - The amount of nutrient depends on what the other parent contributes SLIDE 27 - All gametes are roughly the same size, but there’s chances that there’s some that produces smaller and larger gametes - Those producing larger gametes stand better chance because there’s more nutrients - The smaller gametes requires less investment - Mid size aren’t favoured at all - So eventually, it’s just two sizes - Larger gametes take on the nurturing role - Smaller gametes take a more exploiting strategy - That’s how females and males are differentiated because there’s always going to be one that produces smaller gametes and some producing larger gametes SLIDE 28 - At least one has to be able to move (sperm because they’re small) - Sperm are cheap to make because there’s no nutrients in them so they can produce more SLIDE 29 - Both males and females features are called hermaphrodites - They can’t self-fertilize, because they nullify the benefits of sexual reproduction so they have safety NOTE: DUE TO POTENTIAL COPYRIGHT INFRINGEMENTS, THE SLIDES HAD BEEN TAKEN OUT BY OWNER. mechanisms to ensure not to have self fertilization - Producing different gametes at different times of the seasons; producing in different areas of the body; SLIDE 30 - There aren’t more than two sexes - The closest thing is that different sex can have different reproductive roles - In bees, only one fertilizing female at any given time, the rest are sterile - The brightly colour male is the reproductive male and the rest are drab in colour, until the colour one dies, another one changes physically and takes its place SLIDE 31 - Sex ratio is almost close to equal in males and females 1:1 because people usually pair up 1 to 1 - Langur monkey: dominant monkey has a harem of 12 monkeys - Elk: one bull controls up to 60 females - That means some males are sterile and never get to reproduce SLIDE 32 - What if 10 females born to 1 male so that each male would have a harem SLIDE 33 - Males are more vulnerable than females - Males more likely to die because greater disease susceptibility and higher risk taking behaviour - Excess of females so that means it would be beneficial to have attractive sons - There are actually more males born to females 104-107 sons/100 females SLIDE 34 - Whether embryos become male or female SLIDE 35 - Determined by chromosomes it possesses - Humans have 46 chromosomes - 22 pairs are autosomes and 1 pair are sex chromosomes (X or Y from each parent) SLIDE 36 - don’t have sex chromosomes - Determined by the temperature of the eggs - It depends on the species - Turtle: higher temperature = females; lower temperatures = males - alligators: higher temperature = males; lower temp = females - Snapping turtles = low temp = females; intermediate temp = males SLIDE 37 - Species evolved adapted to their environment and usually the same to both males and females - Peacocks and hens look different from each other; male peacocks doesn’t allow for greater survival but for looking pretty and attracting females - Sexual selection: the traits evolve in competition for mates - Intrasexual: between the males competing against each other - Intersexual: the selecting females choosing certain males SLIDE 38 - Males and females have different reproductive strategies
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