Biology I Study Guide Classes 1-8 PDF

**1. How does natural selection work?** Three components of natural selection - Variation - Inheritance - Differential Reproductive Success Scientific process - What was Hopi's hypothesis? - Natural selection has resulted in coat color matching the local environments whe...

**1. How does natural selection work?** Three components of natural selection - Variation - Inheritance - Differential Reproductive Success Scientific process - What was Hopi's hypothesis? - Natural selection has resulted in coat color matching the local environments where the mice live - What alternative explanations could there be? - Maybe coat color is environmentally determined (sun exposure, diet, mice chameleons?) - What were the predictions of that hypothesis? - Variation: There is variation in coat color within populations (or was at some point) - Inheritance: There is genetic variation that is associated with variation in coat color - Differential reproductive success: Mice with coats that do not match their environment are more susceptible to predators - How did she test those predictions? - Variation - Figures 3.5 and 3.6 in the reading - [[https://youtu.be/uM4LxBG74ag?t=208]](https://youtu.be/uM4LxBG74ag?t=208) (stop at 4:04) - Inheritance - Figure 3.7 in the reading - [[https://youtu.be/uM4LxBG74ag?t=1225]](https://youtu.be/uM4LxBG74ag?t=1225) (stop at 22:57) - Differential Reproductive Success - Figure 3.10 in the reading - [[https://www.youtube.com/watch?v=uM4LxBG74ag&t=456s]](https://www.youtube.com/watch?v=uM4LxBG74ag&t=456s) (stop at 12:15) - How did the results feed back onto her view of that hypothesis? - All of the predictions were verified, which lent support to the hypothesis. **2. How does an organism get fit?** Life History Traits as Components of Fitness - Life history trait - Any trait that affects survival or fecundity at any age - Energy is limited and must be allocated to one function or another - Maintenance, survival, reproduction - A trade-off is the idea that allocation of energy to one function comes at the cost of not allocating it to another function Costs of Reproduction - Figure 11.3 in the reading - Hypothetical traits that affect the flow of energy to function in different ways - With A, some types are just better than others, because they increase the energy input and so different values do not present a trade-off - With B, a trade-off is inherent, because different values of B result in benefits in one respect but costs in another Fitness in Age-Structured Populations - Life table - l~x~ = probability of surviving through age x - m~x~ = fecundity at age x - l~x~ m~x~ = expected reproduction at age x - R~0~ = sum l~x~ m~x~ = lifetime reproductive success - T = sum x l~x~ m~x~ / R~0~ = generation time - r = ln(R~0~) / T = intrinsic rate of increase - Exercise: Compute fitness with life table - Two examples, same R but different T and r - R~0~ = 1.4, T = 3.357, r = 0.10 ------ ------ l~x~ m~x~  0.9 0 0.5 0 0.3 3 0.1 5 ------ ------ - R~0~ = 1.4, T = 2.43, r = 0.14 ------ ------ l~x~ m~x~  0.9 0 0.8 1 0.6 1 0.1 0 ------ ------ - Explore the consequences of these different intrinsic rates of increase Diverse Life Histories - Are organisms always better off if they reproduce sooner? - Not necessarily - Many organisms have increased fecundity at older ages because their bodies continue growing as they age (e.g., plants and fishes). - Some organisms might be better parents as they age due to more experience or by helping out as grandparents (e.g., mammals). - Mortality is often high for young organisms, so rather than invest in early reproduction it may be more beneficial to allocate resources towards surviving through those early stages and/or growing faster. **3. What is the role of chance in evolution?** - - - - - - - - - - - - - - - - - 1. 2. 3. - - - - - - - - - - - - - - - - - - **4. What is a phylogeny?** - - - - - - - - - - - - - - - - - - - **5. What can phylogenies tell us about how traits have evolved?** - - - What is the date of a most recent common ancestor of a group of organisms? - What was the geographic history or path of the ancestors of a group of organisms? - What is the date of a most recent common ancestor of a group of organisms? - The specific question here is when humans started wearing clothes. - The idea is that humans would not have had body lice until they started wearing clothes, because clothes help provide shelter for body lice. - A phylogeny of chimp lice, human head lice, and human body lice shows that the two types of human lice are distantly related to the chimp lice. It also shows that the body lice evolved from the head lice more recently. - To figure out the timing of these events, we apply a molecular clock. This is an assumption about how long it takes for genetic changes to occur between lineages that separated at some time in the past. It implies that genetic changes accrue at similar rates along divergent lineages of a phylogeny. - To calibrate the molecular clock, we need at least one internal node on the phylogeny with a known date, so we can say how long it took for a given number of genetic changes to occur along a lineage. - You should understand the simplified example of how this works on slides 7-9. - What was the geographic history or path of the ancestors of a group of organisms? - The specific question here is how did a chameleon cross the Indian Ocean. - First, we talked about the geologic history of the continents and subcontinents and islands involved: Africa, Madagascar, Seychelles, India. You do not need to know this history, but it is an important part of understanding the example. - The geologic history of these continents and subcontinents and islands resembles that of a biological phylogeny. They started out in the past as one and, over time, split off from that common ancestral lineage one at a time. - The key question here about the chameleon is in what order did its lineages split off from its common ancestral lineage. The present-day chameleon lineages of interest correspond to different geographic areas where the chameleons occur (chameleons in Africa, chameleons in India, etc.). - One hypothesis is that the phylogenetic history of the chameleons mirrors that of the geologic history. If the chameleons just stayed put as the continents, subcontinents, and islands split, their phylogeny would be identical to the geologic history. - A second hypothesis is that the chameleon colonized the Seychelles from Africa. Any phylogeny in which chameleons from the Seychelles and Africa are sisters would be consistent with this hypothesis. - A third hypothesis is that the chameleon colonized the Seychelles from India. Any phylogeny in which chameleons from the Seychelles and India are sisters would be consistent with this hypothesis. **6. What can phylogenies tell us about how a species has evolved?** - - - - - - - What do the number of dice correspond to biologically? - What does the number of sides of the dice correspond to biologically? - What does it mean when two dice come up with the same number? - - Randomness in reproductive success results in variability in coalescence times. - Coalescence events happen faster when there are more lineages. Once it is down to two lineages, it can take a relatively long time for coalescence to happen. - Coalescence happens faster in smaller populations and slower in larger populations. - In a population that has experienced growth over time, coalescence events happen more slowly in the recent past and more quickly in the distant past. - In a population that has experienced decline over time, coalescence events happen more quickly in the recent past and more slowly in the distant past. - - Prediction involves going from an assumed population size and saying how long we expect coalescence to take. - Inference involves going from a set of observed coalescence times and using that to determine how big a population's size is. - Both prediction and inference can be done with either constant population sizes or with population sizes that vary over time. - Know the steps to inferring population size. You do not need to know the mathematical formulas. They are included just to show you that there is a mathematical basis to making these inferences. - Application of the coalescent model - This paper used 6 human genome sequences together with the coalescent model to infer how the human population size has changed over the past couple hundred thousand years. **7. How do new species arise?** **8. Is evolution predictable?** 1. What are key differences among anoles that live in: i) grasses and shrubs, ii) on the ground, iii) lower in trees, and iv) higher in trees? 2. How did the scientists test the hypothesis that the differences among the lizards were adaptations to their environments? 3. What happened when the scientists placed tree-dwelling lizards on a barren island with no other lizards? 4. How did these lizards speciate in such close proximity of each other? 5. How did the scientists estimate the patterns of relatedness of the different lizard species? 6. How did the scientists infer that the same types of lizards evolved independently on each island? 7. Why are there so many species in the world? 8. Do you think evolution is predictable? Explain.