BIOLOGY 101 FINAL STUDY GUIDE EVOLUTION AND BEHAVIOR Behavior has value - Animals maximize energy consumed and minimize energy used - Humans like foods high in fat and sugar; the more the fat, the stronger the preference - There is a limit to sugary preference, while the preference for fat continues to increase as fat content increases Why Have Taste Preferences? - Feeding choicDon't forget about the age old question of eurakyote
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es directly influence fitness - Living and reproducing require energy - Maximal extraction of energy and acquisition of essential nutrients - Natural selection can shape feeding behavior - Cost vs benefits Behavior - Is defined as any and all of the actions performed by an organism - Often in response to its environment or to the actions of another organism - Many behaviors influenced by natural selection Role of the Environment - The degree to which a behavior depends upon the environment varies - Instincts or innate behaviors - Example: fixed action pattern that is triggered under certain conditions ⇨ Requires no learning ⇨ Does not vary ⇨ Once started, runs to completion Learning - involves behaviors that are altered and modified over time in response to past experiences - tremendous variation among behaviors that require learning ex. primates – fear of snakes (prepared learning) Prepared Learning - Behaviors that are learned easily and by all (or nearly all) individuals - Snake-fearing behavior of monkeys - Acquisition of language in humans - Fear of snakes “old”, fear of guns “new” - “don’t touch the hot kettle” Complex Behaviors - why do animals have sex? - Why do people have sex? - Ex. geese retrieving egg-shaped objects in order of size ALTRUISTIC Behaviors - Behaviors that come at a cost to the individual doing the behavior while benefiting the recipient - Darwin’s theory generally works to produce selfish behaviors:⇨ Kin selection ♦ You are more likely to help relatives that carry your genes, rather than complete strangers who don’t ♦ Hamilton’s Rule: Altruistic-appearing behavior occur when the benefits to close relatives are greater than the cost to the individual ♦ Ex. female Belding’s ground squirrel make alarm calls to alert predator’s presence; harms the individual but protects the rest of the squirrels ⇨ Reciprocal altruism: help others in exchange for future help ♦ Requires 3 conditions to be met: 1) Repeated interactions among individuals 2) The benefits to the recipient must be significantly greater than the costs to the donor 3) The ability to recognize and punish cheaters Redefining Fitness - Direct fitness ⇨ An individual’s total reproductive output - Indirect fitness ⇨ The reproductive output brought about the altruistic behaviors toward close kin - Inclusive fitness ⇨ The sum of an individual’s indirect and direct fitness Conflicts - Different individuals do not share all of the same alleles, we should always expect some conflict - Example: gestational diabetes ⇨ Fetus produces chemicals that increase the diameter of the mother’s blood vessels (increasing the amount of food the fetus gets). In response the mother produces insulin, reducing the amount of sugar in the bloodstream = gestational diabetes ECOSYSTEMS AND COMMUNITIES Trophic Levels - All energy starts with the sun - Use ~1% - 4 levels - 90% loss Energy flow within an ecosystem - energy from the sun is intercepted and converted into chemical energy, which passes through an ecosystem in about four stops/ levels 1) PRODUCERS - Plants convert light energy from the sun into food through photosynthesis 2) PRIMARY CONSUMERS - Herbivores are animals that eat plants 3) SECONDARY CONSUMERS - Carnivores are animals that eat the herbivores 4) TERTIARY CONSUMERS - Top carnivores are animals that eat other carnivores Chains or Webs? - Food chain ⇨ Direct pathway from photosynthetic produces - Food web ⇨ Involve harvesting energy from multiple stops in the food chain Recyclers - When they die, organisms from every level in the food chain provide sustenance for decomposers and detritivores, and important chemical components are recycled through the food chain - Decomposers and detritivores (ex. dung beetle) break down organic wastes, releasing chemical components that can be reused by plants and other producers - Essentially feed at all trophic levels 1) Decomposers ⇨ Bacteria or fungi 2) Detritivores ⇨ Scavengers Biomass - The total weight of all the organic material in a given area - 10% rule: remaining 90% expended in cellular respiration or lost as feces 10% Rule - only about 10% of the biomass from each trophic level is converted into biomass in the next trophic level- rest of available energy is lost to the environment, a consequence of several factors ( non predatory deaths, incompletely digestion of prey/food, respiration) - the inefficiencies in the transfer of energy from one trophic level to the next explain why there are so many more plants than animals Variations in Primary Productivity ⇨ Large-based Pyramid ♦ Supports a relatively large biomass of consumers ♦ Common in rainforests, marshes and algal beds ⇨ Small-based Pyramid ♦ Reduced ability to support consumers ♦ Common in deserts, tundras, and open oceans ⇨ Inverted Pyramid ♦ Small biomass of producers supports a relatively large biomass of consumers ♦ Occurs in some aquatic ecosystems where plankton are producers NICHE: the full range of conditions under which it may live - An organism’s place in the community, including its complete way of living 1) The space an organism requires 2) The type and amount of food an organism utilizes 3) The timing of an organism’s reproduction 4) An organism’s temperature and moisture requirements and other necessary living conditions 5) The organisms for which it is a food source 6) Its influence on competitors Natural Selection - Causes organisms to become better adapted to their environment - Does not distinguish between biotic and abiotic resources as selective forces - Coevolution ⇨ Two (or more) traits evolved alongside each other Competition: when niches of two species overlap - Competitive exclusion ⇨ One species within the niche utilizes resources more efficiently, driving the other species to local extinction - Resource partitioning ⇨ Each species alters its use of the niche, dividing the resources Character Displacement - A special case of resource partitioning - Occurs when natural selection reduces competition between two species by producing an evolutionary divergence in one or both species - Character displacement is an evolutionary adaptation that makes resource partitioning possible- Example with the finches and their beak sizes Predation is one of the most important forces shaping the composition and abundance of species in a community - Two broad categories of defenses against predators: 1) Physical 2) Behavioral Physical Defenses - Includes mechanical, chemical, warning coloration, and camouflage mechanisms 1) Mechanical Defenses - Physical structures (ex. quills of a porcupine) can help protect from predation 2) Chemical Defenses - Toxins (ex. strawberry poison dart frog) can make an organism appear poisonous to a predator 3) Warning Coloration - Organisms that produce toxic chemicals (ex. monarch butterflies) frequently have bright color patterns, warning potential predators to stay away 4) Camouflage - Cryptic coloration (Ex. praying mantis) can enable organism to blend into its surroundings and avoid predators Behavioral Defenses - Include both seemingly passive and active behaviors: hiding or escaping, or alarm calling and fighting back Predator Adaptations - Toxic-avoidance methods - Better sensory perception - Mimicry - The “life-dinner” hypothesis Parasites - Predators that benefit from a symbiotic relationship with their hosts - Ectoparasites (ex. bedbug) live on their hosts - Endoparasites (ex. trypanosoma brucei) live inside their host Mutualism - Both species benefit from an interaction - Ex. bees and flowers Commensalism - One species benefits from an interaction and the other neither benefits nor is harmed - Ex. cattle egret and buffalo POPULATION ECOLOGY Ecology - The study of interactions between organisms and their environments - It is studied on many levels, including: ⇨ Individuals ⇨ Populations ⇨ Communities ⇨ Ecosystems Population Growth - Stable Populations: each individual ultimately replaces itself with a new individual - Linear Growth: the population increases by a set number of individuals per year - Exponential Growth: the population increases at a rate proportional to its size ⇨ occurs when each individual produces more than the single offspring necessary to replace itself ⇨ populations cannot grow unchecked forever, so exponential growth never lasts long in nature Determining How a Population Grows (or Shrinks) - Growth rate = r - Number of individuals in population = N Population Limitations - Reduced food supplies due to competition - Diminished accessibility to places to live and breed - Increased incidence of parasites and disease - Increased predation risk Carry capacity, k= limits on growth of a population ⇨ Increased death rate ⇨ Increased emigration rate ⇨ Reduced birth rate Logistic Growth describes population growth that is gradually reduced as the population nears the environment’s carry capacity Maximum sustainable yield: the removal of as many individuals as possible without impairing the population’s growth - The point at which the maximum number of individuals are being added to the population Variations in Life Histories - Big-Bang Reproduction (antechinus) ⇨ Reaches sexual maturity at one year ⇨ Mates intensely over three-week period ⇨ Males die shortly after mating period⇨ Females usually die after weaning their first litter - Slow, Gradual Reproductive Investment (little brown bat) ⇨ Reaches sexual maturity at one year ⇨ Produces about one offspring per year - Fast, Intensive Reproductive Investment (house mouse) ⇨ Reaches sexual maturity at one month ⇨ Produces litters of six to ten offspring every month Evolutionary Constraints - Ideal organisms would produce many offspring, grow tremendously large and live forever - Evolutionary tradeoffs Survivorship Curves - Shows the proportion of individuals of a particular age that are alive in a population ⇨ Type I ♦ High survivorship until old age, then rapidly decreasing survivorship ⇨ Type II ♦ Survivorship decreases at a steady, regular pace ⇨ Type III ♦ High mortality early in life, but those that survive the early years live long lives Biological species concept: species can interbreed with each other, cannot interbreed with organisms outside their own group - Sterile offspring Barriers to reproduction 1. Prezygotic barriers ⇨ Individuals physically unable to mate with each other ⇨ If individuals are able to mate, the male’s reproductive cell is unable to fertilize the female’s reproductive cell 2. Postzygotic barriers ⇨ Matings produce hybrid individuals that do not survive long after fertilization ⇨ If hybrid offspring survive, they are infertile or have reduced fertility Linnaeus and systema naturae 1. Genus 2. Specific epithet Ex. Homo sapiens - Each species on earth is given a specific name and is categorized according to hierarchical groups ⇨ DOMAIN ⇨ KINGDOM ⇨ PHYLUM⇨ CLASS ⇨ ORDER ⇨ FAMILY ⇨ GENUS ⇨ SPECIES ⇨ Dear King Philip Came Over For Great Spaghetti - The biological species concept is remarkably useful when describing most plants and animals, but it doesn’t work for distinguishing all life forms ⇨ Classifying asexual species ⇨ Classifying fossil species ⇨ Determining when one species has changed into another ⇨ Classifying ring species (non-interbreeding population) ⇨ Classifying hybridizing species Morphological Species Concept - A common alternate method of defining separate species, focusing on morphology - Focus on aspects of organisms other than reproductive isolation as defining features - Characterizes species based on physical features such as body size and shape - Can be used effectively to classify asexual species Microevolutionary changes in allele frequencies in a population over time can lead to macroevolution, changes on a grand scale, including vast diversification of species ⇨ MACROEVOLUTION: the accumulated effect of microevolution over a long period of time ⇨ MICROEVOLUTION: a slight change in allele frequencies over one or a few generation - Evolution is one thing only: a change in allele frequencies within a population(microevolution). But over time, these changes can lead to a new species and groups of species that vary tremendously (macroevolution). Punctuated Equilibrium - Long periods of relatively little evolutionary change punctuated by bursts of rapid change - The tempo of evolution varies for different species - Gradual Change ⇨ Evolution by creeps: the pace of evolution occurs gradually in incremental steps - Punctuated equilibrium ⇨ Evolution by jerks; long periods of relatively little evolutionary change are punctuated by bursts of rapid change Adaptive Radiations - Occurs when a small number of species diversify into a larger number of species, from the following: ⇨ Mass extinction events⇨ Colonization events ⇨ Evolutionary innovations Two categories of extinction - Mass extinction ⇨ A large number of species become extinct over a short period of time due to extraordinary and sudden environmental change - Background extinction ⇨ These extinctions occur at lower rates during times other than mass extinctions EVOLUTION & NATURAL SELECTION Darwin - Pre-Darwin, all religion - Wasn’t solely Darwin that changed people’s viewpoints Darwin’s Journey - University of Edinburgh, medical studies - Studied theology at Cambridge University - Real love = study of nature - Traveled on the Beagle… 1st: Darwin’s finches 2nd: Fossil resemblance to living organisms Resemblance of island finch species to mainland finch species - Although the finches found on the Galapagos Islands had slightly different physical characteristics, they still resembled the single mainland finch - Difference in beak sizes Resemblance of extinct species to living species in same area - Around the world, there is a striking similarity between the fossils of extinct species and the living species and the living species in that same area DARWIN’S THEORY OF EVOLUTION - Essay of the Principle of Population by Thomas Malthus - The Origin of the Species - Changed the way we think about the world Evolving Beliefs in Darwin’s World// Darwin’s Origin of Species Before: - All organisms were put on earth by a creator at the same time - Organisms are fixed; do not change or evolve - Earth is about 6,000 yrs old After: - Organisms change over time (evolve) - Some organisms have gone extinct - Earth is more (definitely more) than 6,000 yrs. old- The geology of Earth is not constant, but always changing Populations Evolve, not individuals - Evolution is a change in the allele frequencies of a population over time Mechanisms of Evolution - Mutation (only really matters in reproductive cells, occur during cell division) ⇨ An alteration of the base-pair sequence in the DNA of an individual’s gamete producing cells that changes an allele’s frequency ⇨ Mutations almost always cause early death or lower reproductive success of an organism - Genetic Drift ⇨ A random change in allele frequencies, UNRELATED to any allele’s influence on reproductive success ⇨ So neither allele is related to reproductive success, inheritance is based solely on chance ⇨ Founder Effect ♦ Small number of individuals start a new, isolated population ♦ When founding members of new population have different allele frequencies than the original source population ⇨ Bottleneck Effect ♦ Genetic drift occurs via bottleneck effect when famine, disease, or rapid environment change causes the deaths of a large portion of the population, and the surviving individuals have different allele frequencies than the original population ⇨ Genetic drift leads to fixation when an allele’s frequency becomes 100% in a population => no longer genetic variation for the gene - Migration ⇨ A change in allele frequencies caused by individuals moving into or out of a population - Natural Selection ⇨ A change in allele frequencies that occurs when individuals with one version of trait have greater reproductive success than individuals with a different version of the trait ⇨ Three conditions required: 1) Variation within a population 2) Variation must be inheritable 3) Differential reproductive success DIFFERENTIAL REPRODUCTIVE SUCCESS - Darwin’s 3 observations 1) There are more organisms born that can survive 2) Organisms are continually struggling for existence 3) Some organisms are more likely to win this struggle and survive/reproduce than others (natural selection) When all three conditions are satisfied, the population’s allele frequencies change and, consequently, evolution by natural selection occurs HARDY-WEINBERG LAW- A trait won’t simply decrease in frequency simply because it is recessive - Use Hardy-Weinberg Equation to predict how common each genotype in the population will be 2pq= frequency of heterozygotes 1000 individuals= 2000 alleles If a population is in Hardy Weinberg equilibrium, and the allele frequencies of the population are known, predictions can be made about the genotypes of the offspring As long as there is random mating and no evolution, the frequencies of recessive alleles and dominant alleles do not change over time - Applies only when there is: ⇨ No natural selection ⇨ No mutations ⇨ No migration ⇨ No genetic drift ⇨ Random mating FITNESS - A measure of an organism’s reproductive success - 3 important elements: 1) relative to other genotypes or phenotypes in the population 2) depends on environment 3) depends on organism’s reproductive success compared to the other organisms Adaptation - the process by which organisms become better matched to their environment and the specific features that make an organism more fit Perfect organisms don’t exist - constant changing environments don’t produce perfection (CAN’T) - three factors that prevent perfection 1) Environments change quickly 2) Variation is needed as the raw material of selection 3) There may be multiple different alleles for a trait, each causing an individual to have the same fitness Trait Categorization - Specific category ⇨ Some traits can be easily placed into one category or the other - Continuous Range ⇨ other traits, such as height, may fall into a wide range of valuesDirectional Selection - individuals with one extreme from the range of variation in the population have higher fitness ⇨ selectively breeding for large milk production ⇨ selectively breeding for large breasts in turkeys Stabilizing Selection - individuals with intermediate phenotypes are most fit ⇨ ex. babies with low birth weights are more vulnerable to complications, but babies with high birth weights are also more vulnerable to complications (selective pressure) Disruptive Selection - individuals with extreme phenotypes experience the highest fitness, and those with intermediate phenotypes have the lowest Complex Traits - the ability to learn quickly or slowly is a genetic trait