Biology and Ecology 2602 Notes- Week 1
Biology and Ecology 2602 Notes- Week 1 40053
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This 4 page Class Notes was uploaded by Sara Notetaker on Sunday September 4, 2016. The Class Notes belongs to 40053 at Youngstown State University taught by Dr. Renne and Dr. Walker in Fall 2016. Since its upload, it has received 90 views.
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Date Created: 09/04/16
Biology 2602 Notes- Week 1 Every organism has a “choice” to allocate resources to either survive or reproduce. 2 successful offspring are needed to “breakeven” in a Darwinian outlook for 2 reproducing offspring **Exam Question: o Forcing a population to delay its reproduction increases the mean longevity of individuals over time...The greater the delay, the longer the individuals will live. What is the mechanism(s) underlying this phenomenon? 2 mechanisms: Genetic: it’s hard for natural selection to eliminate genetic conditions expressed later in life – so these conditions are passed on. Physical: Darwinism (reproduction is costly) o More resources to reproduce less resources to survive Only thing that natural selection operates on is genetic variation Natural Selection- when it operates- pushes a population in a particular direction 100% of the time. Ecology- the scientific study of how biotic and environmental interactions (abiotic) affect the distribution and abundance of organisms (and biochemical processes) Biological Evolution- the process of change in the inherited traits of a population of organisms from one generation to the next (decent with modification.) Microevolution- a change in allele frequency in a population overtime o Underlying mechanisms 1. Change in the environment 2. Change in population (Genetic Drift) 3. Migration 4. Mutation 5.Assortive Mating Artificial Selection- The breeding of plants and animals to produce desirable traits. Natural Selection’s 3 components: o 1. More individuals are produced that can possibly survive (ALL species have potential for exponential growth) o 2. There must be ecological factors that hold the population size in check Finite resources cause constrain on population growth o 3. Heritable traits that increase an individual’s rate of survival and/ or reproduction will tend to spread throughout the population. Directional Selection- consistent differential survival and/ or reproduction in a single phenotype. **Individuals are selected- populations evolve. Population- a group of conspecific organisms that frequently interbreed with each other and share the same geographic range (the latter differs widely among species.) Biological Species Concept (BSC)- “species are group of actually or potential interbreeding natural populations, which are reproductively isolated from other such groups” (Mayr 1942.) o 3 components of BSC 1. Actual/potential breed 2.Natural population 3.Reproductively isolated from the other group. BSC is highly criticized Hardy-Weinberg Theorem Assumptions: o 1. The population is very large Chance effects of allele frequency changed are thus greatly reduced o 2. Matings are random Individuals show no mating preference for a particular genotype or phenotype o 3. There are no net changed in the gene pool due to mutation Mutation from A to a equals a to A o 4. There is no migration of individuals into and out of the population o 5. There is no selection; all genotypes are equal in survivorship and reproductive success When all of the HWT Assumptions are met there is NO MICROEVOLUTION o Microevolution is the normality Individuals don’t evolve POPULATIONS do. Natural Selection (which has 3 key components) 1. More individuals are produced than can possibly survive (all species have potential for exponential growth) 2. There must be ecological factors that hold the population size in check 3. Heritable traits that increase an individual’s rate of survival and/ or reproduction will tend to spread throughout the population. Natural Selection- differential survival and/ or reproduction among entities that differ in one or more heritable characteristics. If selection occurred and we didn’t see large population response trait not very heritable Types of Natural Selection o 1. Directional Selection- consistent differential survival and/ or reproduction in a single phenotype that is above or below the current mean. “cost of resistance” and “Use it or lose it” o 2. Stabilizing (or Balancing) Selection- consistently higher survival and/ or reproduction in the intermediate phenotype. o 3. Diversifying (or Disruptive) Selection- consistently lower survival and/ or reproduction in the intermediate phenotype. A necessary condition for sympatric speciation (Speciation in the same area) Genetic Drift- process of RANDOM change in allelic frequency over time. Aka genetic stochasticity Larger population lower strength of genetic drift Founder Effect- genetic composition of founding population Genetic Bottle Neck- occur when process of population reduction- cases a loss of genetic variation. Speciation- process by which a new species is created. o Key component: REPRODUCTIVE ISOLATION Reproductive Isolating Mechanisms: o Pre-zygotic Isolating Mechanism: Geographic Isolation Species in different places Ecological Isolation Species use different resources in habitat. (Local adaptations to plant species) Behavioral Isolation- Species have different mating rituals Temporal Isolation- mating/lowering at different times (insert mating attempt) Mechanical Isolation- structural differences prevent mating/ pollen transfer Gamete Fusion Prevention- gametes fail to attract (chemical) o Post-zygotic Isolating Mechanism Hybrid embryos do not develop properly Hybrid adults do not survive in nature Hybrid adults are sterile or have reduced fertility Natural Selection and Speciation o In this case, natural selection will strongly favor matings within genetically similar groups- this reinforces pre-zygotic isolation mechanisms by avoiding wasted efforts In most species strongest pressure is for females to choose wisely Types of Speciation o Allopatric Speciation- Separation by geography o Polyploidy Speciation- “instantaneous speciation”- meiotic failure Mostly in plants o Sympatric Speciation- Same region speciation Disruptive selection Local adaptations Phylogeny- evolutionary tree Family trees, etc.
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