Upgrade to remove ads
Only $2.99/month

BILD 3 Study Guide

Terms in this set (87)

Describe the two main tenets of Darwin's Origin of Species, and know what year the book was published
Descent with Modification and Natural Selection; 1859
Describe the prevailing view regarding evolution and species in Europe in the 1800s
Old Testament account of creation, which holds that species were individually designed by God and therefor perfect
Identify and explain the main discoveries of the following scholars: Linnaeus, Hutton,
Lyell, Cuvier, Malthus, Lamarck. Be able to evaluate the impact of each of these scholars on Darwin
Linnaeus: Nested classification system, grouping similar species into increasingly general categories. Darwin argued that classification should be based on evolutionary relationships.
Hutton: Earth's geological features could be explained by gradual mechanisms.
Lyell: The forces observable today can create what we see around us, given enough time.
Both Hutton and Lyell got Darwin thinking that the Earth was older than people thought.
Cuvier: Opposed evolution, speculated each layer of strata was from different catastrophic events.
Malthus: Much of human suffering-disease, famine, war- resulted from the human population's potential to increase faster than food supplies and resources.
Lamarack: The parts of the body that are used extensively become larger and stronger, while those that are not deteriorate.
Darwin thought that variation was introduced into the evolutionary process in part through inheritance of acquired characteristics.
Describe what nested hierarchical categorization of organisms means, and identify whether or not this type of organizational system is still in use today
Nested: grouping similar species into increasingly general categories.
It is still used today
Define the hypothesis of gradual geologic change, name its proponents, describe its predictions about the age of the Earth, and discuss the evidence to support it that Darwin found on his voyage
Geologic change results from slow, continuous actions; Predicts that Earth is over a million years old, Darwin found evidence from the earthquakes in Chile
Explain Lamarckian evolution, and be able to give an example of how this mechanism was hypothesized to lead to change. Evaluate Lamarck's views in light of current biological knowledge
Proposed a mechanism for how life changes over time
Believed that evolution occurs because organisms have an innate drive to become more complex
Lamarack was right to recognize that organisms are well suited for life in their environments, which can be explained by gradual evolutionary change
Describe the biogeographical patterns Darwin observed on his voyage and explain how they provide support for the theory of evolution
Species are similar because they are related ---> Similar because of common ancestry
Different selection pressures on each island gave rise to different local adaptations via natural selection ---> Different because of local adaptation; Branching pattern (divergence)
Tortoises, finches
Geologic change occurred when an earthquake shook the coast of Chile, and he found ocean organism's fossils up in the Andes (starts to see the world through Lyell's eyes); Physical evidence did not support the traditional view that the earth was only a few thousand years old
Describe the lines of research Darwin did upon his return to England in 1836, and assess how each of these projects contributed to his views (as described in The Origin of Species)
He tried to find evidence of his ideas: studied barnacles & wrote 4 books on them), bred pigeons (artificial selections), studied how organisms dispersed
Describe the process of adaptive radiation that led to many Galapagos finches with different beaks
The finches' s rapidly diversified from their ancestral species to have a multitude of new beak forms; a change in the environment made new resources available (food), created new challenges, or opened new environmental niches finches'
Explain Wallace's independently developed ideas about the origin of species, including the biogeographical patterns that led him to those conclusions. Discuss why Darwin
receives the bulk of the credit for the idea of natural selection
Naturalist working in the South pacific islands of the Malay Archipelago; Darwin had developed and tested the idea of natural selection so extensively
Noticed a pattern in the Malay Archipelago
Isolation + time ---> divergence
Older islands have more endemic species (only found in that particular area)
Geographic barriers promote divergence
Every new species arises close to and existing at the same time as another spices that looks a lot like it = his model for how new species form
Demonstrate how Darwin's observations on his voyage led to major inferences in The Origin of Species
He saw local adaptation to fit the local environment; he realized that different islands supported distinct species and subspecies within certain lineages (tortoises)
Earthquake in Chile inferred the earth's age, adaptations of the finches centered on natural selection
Discuss the response to the publication of The Origin of Species: which ideas were readily accepted, which were not, and why
Within a decade, his book and its proponents had convinced most scientist's that life's diversity is the product of evolution.
Descent with modification was widely, readily accepted.
Natural Selection was not because it rejected religion, did not think Earth was old enough to create the diversity, not clear how traits were passed down to descendents
Identify the future knowledge that helped garner widespread support for natural selection within the scientific community
Today: The origin of flowering plants is now better understood, fossils have been discovered that signify the origin of new groups of organisms, natural selection can cause rapid evolution in a wild population
Now we know that the Earth is very old, we have a better understanding of genetics and how traits are inherited
Provide examples of various different types of evidence for evolution, and how each of these is used to demonstrate the occurrence of evolution.
the fossil record of change in earlier species
the chemical and anatomical similarities of related life forms
the geographic distribution of related species
the recorded genetic changes in living organisms over many generations
Differentiate between microevolution and macroevolution. Which type of evolution was Darwin thinking about when he described descent with modification?
Microevolution: small scale changes in allele frequencies, short time scales (Change in the genetic composition of a population across generations) (Galapagos Finches)
Macroevolution: change in the composition of species over time (Descent with Modification) (Evolution of Whales)

Microevolution + a lot of time = macroevolution
Explain the principle of stratigraphy and how it results from the process of how sedimentary rock and fossils are formed.
Principle of stratigraphy: Older organisms are on top. Strata is compressed new layers of rock that occur when new sediment covers older ones
Explain how fossils can be used as evidence for evolution (including demonstrating extinction, succession, and transitional forms).
Fossils are the remains/trace of organisms from the past. The fossil record shows that over time, descent with modification produced increasingly large differences among related groups of organisms, creating diversity. Transitional = Tiktaalik
Describe the hypothesis that Tiktaalik's discoverers were testing when they searched for a transitional tetrapod in 375 million year old rocks.
Reconstructing how fins become progressively more limb-like over time
List several ways in which Tiktaalik resembles modern tetrapods and ways in which it resembles fish.
Tetrapods: neck could move independently of its body, rib bones, lungs, functional wrist joint (one bone, then two bones, then a set of small bones)
Fish: sharp teeth like a predator, flat skull, eyes on top of head, spiracle, gills, scales, fins, fish like fins instead of toes
Be able to explain why transitional fossils are not necessarily direct ancestors of modern organisms, but rather cousin-like. How does this relate to the "shape" of the tree of evolution (i.e. is it a straight ladder, or a tree with many branches)?
Transitional fossils are any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. Tiktaalic was the transitional fossil between land and water organisms
List some vestigial structures in humans and the functions they served in our ancestors.
Appendix, Tailbone (Tails), Wisdom Teeth (wide jaws)
Every hair on our body has muscles that make the hair stand up, creating goosebumps, pretty useless in us (leftover from ancestors with denser hair)
Define homology, and explain how different types of homology (molecular, structural,
developmental) can reveal common evolutionary origins.
Homology is similarity due to common descent; the structure is recognizablly similar, but the function, the role it plays, is different; structure similar due to descent, function different due to natural selection
Developmental Homology: Inherited similarities during development, despite differences in adults
Molecular Homology: Similarities among organisms at the molecular level; genetic code is in all organisms, the same codons (triplets) specify the same amino acid
• National institutes of Health funds research on fruit flies, mice, yeast, bacteria
Homologies let us build evolutionary trees
Compare and contrast homology, vestigial structures, and convergent evolution
(analogous structures). Be able to give an example of each.
A vestigial structure is a structure that was useful in the common ancestor, and is still there, but it is not useful; A functionless structure in one species that had an important function in a related species (wisdom teeth)
Homology is structure similar due to descent, function different due to natural selection (Bee stingers are evolved ovipositors, which is why male bees do not sting (they do not have an ovipositor to store their eggs) (bat wings)
Analogous Structures are from convergent evolution (similar traits that arose independently) rather than common ancestor (butterfly and bird wings)
Be able to give examples of evolution occurring in the modern day.
Bacteria vary in their response to drugs, some bacteria's may have higher survival, can pass that trait to offspring, bacteria population becomes resistant it has evolved (why they tell you to finish the antibiotics even if you feel better after 3 weeks)
Evolution of pesticide resistance; overuse of insecticides has caused many cases of evolved resistance to insects
Using evolutionary reasoning, justify the fact that much of the National Institutes of
Health budget is devoted to research on non-human organisms.
It is useful to test medicine on rats and fruit flies because it is more practical, more ethical, they share 90% genes with humans, homologous anatomy
Compare and contrast artificial and natural selection
Artificial and natural selection are really the same process but one is driven by man and the other is driven by an organism's traits that allow them to survive and reproduce. Artificial selection is when mankind chooses certain traits in plants and animals and breeds to enhance that trait.
Natural selection is also a process where traits are selected for, but that selection is based upon a trait that gives the organism a mating or survival advantage and this allows them to pass down the traits they possess.
Contrast genotype and phenotype. Explain why not all phenotypic variation is inherited.
Be able to give an example of non-heritable phenotypic variation
Phenotype: the characteristics of an organism as a result of genes and the environment (can be determined by genes, the environment)
Genotype: genetic composition of an organism. The alleles an individual has for a gene (Aa) (the genotype for height). fingerprints, retinal and other blood vessel patterns, or muscular physique developed during one's lifetime.
Define the 3 properties of a trait required for it to be subject to natural selection
Variation in a trait
Heritability of the trait
Differential fitness conferred by the trait
Explain why natural selection only causes evolution if the trait under selection is at least partly heritable
In order for it to be passed on to generations, it must be partially a heritable trait or it will not be moved on
Describe the lessons learned from the Galapagos finches and rock pocket mice examples
Directional Selection: an extreme phenotype is the most fit
Explain what fitness is.
Relative Fitness: the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
Given an example of natural selection, be able to identify the trait under selection, whether the trait is heritable, and how fitness changes in the given environment. Be able to predict the outcomes of evolution via natural selection
...
Compare and contrast the 3 modes of natural selection covered in class (directional, stabilizing, disruptive) with regards to which phenotypes are most fit, how the population mean changes as a result of selection, and how genotypic and phenotypic variation change as a result of selection. For each mode of selection, be able to sketch the fitness curve and explain what it means; and generate a graph of how phenotypes change over time. Given a scenario or graph of how natural selection affects a population, infer which mode of selection is at work and predict the long-term consequences of the selection.
Directional: The population mean changes.
The population variation decreases.
Stabilizing: The population mean stays the same. The population variation decreases.
Disruptive: The population stays the same. The population variation increases.
Explain how balancing selection maintains genetic variation. Give examples of two kinds of balancing selection.
Includes heterozygote advantage and frequency-dependent selection.
Maintains polymorphism in the natural selection
Heterozygote Advantage (Malaria resistance in sickle-cell anemia) (Aa better than AA or aa)
Negative Frequency-Dependent
Natural Selection (rarer = more fit)
Define and use correctly the following terms: Hardy-Weinberg Equilibrium, locus, allele frequency, genotype frequency, genetic drift, gene flow, non-random mating
Hardy-Weinberg Equilibrium: law states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
Locus: the position of a gene on a chromosome.
Allele frequency: gene frequency, the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage.
Genotype frequency: the number of individuals with a given genotype divided by the total number of individuals in the population.
Genetic drift: variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce
Gene flow: the transfer of alleles or genes from one population to another.
Non-random mating: occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals
Explain why we test for Hardy-Weinberg equilibrium.
The Hardy-Weinberg Equilibrium shows what the gene pool looks like without evolution
FOR A PARTICULAR GENE
We use it to figure out which of the 5 are going on, all 5 is an ideal situation
Calculate observed genotype frequencies. Calculate allele frequencies using observed
genotype frequencies.
Calculating Geotype Frequencies:
Take the # of individuals who have that genotype (TT, Tt, or tt) and divide by the total #of individuals.
# of TT or Tt or tt/ # of alleles : genotype/alleles
Allele Frequencies:
2(genotype #) + middle genotype / # of alleles
Calculate the predicted genotype frequencies under Hardy-Weinberg Equilibrium.
Compare these with observed genotype frequencies.
Predicted genotype frequencies:
TT: p^(2)
Tt: q^(2)
Tt: (2)(p)(q)
Check math with p^(2) + 2pq + q^(2) = 1
If observed is close to expected, the population is said to be in equilibrium
If observed is significantly different from expected, the population may not be in equilibrium, and may be evolving/mating with not random
List the conditions that must be met for a locus in a population to be at Hardy-Weinberg
equilibrium (assumptions of Hardy-Weinberg Equilibrium theory).
1. No mutations
2. Random mating
3. No natural selection
4. Extremely large population size
5. No gene flow
Apply the Hardy-Weinberg Equilibrium model to provide evidence and justification about whether or not a population is evolving/mating nonrandomly. If its genotype frequencies are not in Hardy-Weinberg equilibrium, offer plausible explanations of how it is evolving/mating nonrandomly (i.e., which condition(s) of HWE are not met) that are consistent with which genotypes are more or less frequent than equilibrium would predict.
Processes that violate the assumptions of HWE:
Mutation
Natural Selection
Non-random mating
Gene flow
Genetic Drift
Compare and contrast genetic drift and gene flow in terms of their impacts on allele and genotype frequencies in populations and their implications for future genetic variation in a population.
Gene Flow:
Allele frequencies can also change by gene flow, the transfer of alleles into or out of a population. Gene flow can result in two populations combining into a single population with a common gene pool. Alleles transferred by gene flow can also affect how well populations adapted to the local environment conditions. It can transfer alleles to improve the ability of populations to adapt to local conditions. Gene flow is an increasingly important agent of evolutionary change in human populations; mating is more common between members of a population, which leads to exchanges of alleles and fewer genetic differences.
Genetic Drift:
Random changes in allele frequencies that are due to random sampling from generation to generations (nothing to do with natural selection). Genetic bottleneck leads to a change in allele frequencies (not considered drift, similar process of random sampling effects changing allele frequencies) it can make the population small, which attracts genetic drift, and then HWE
Explain how genetic drift is a result of sampling effects in finite populations. Explain the main consequences of genetic drift for populations and how the intensity of those effects depends on population size.
Due to random sampling from generation to generations. The consequences include less genetic variation (mice bean lab), and this is more intense when the population is smaller. Smaller populations take less time/generations for all of the species to turn one color/one gene
Describe two ways that populations can become abruptly smaller, intensifying the effect of genetic drift.
Founder effect is small group of people leaving the population to start a new one (allele frequencies might be out of whack compared to original)
Bottleneck effect is when there is a natural disaster and the population goes from like 1000 to 20.
Compare and contrast selection, mutation, drift, and gene flow in terms of their ability to change allele and genotype frequencies in populations, and their relative strengths.
Selection: Most evolution that affects bodies (phenotypes) is governed by natural selection
Mutation: Disrupts the equilibrium of alleles by introducing new alleles into a population
Drift: Allele frequencies grow higher or lower by chance and typically take place in a small population
Gene flow: can transfer alleles to improve ability to adapt to environments, makes mating with members within the population more common, leading to exchanges of alleles and less diversity
Resolve this apparent contradiction of the neutral theory of evolution: Most genetic evolution happens via genetic drift on neutral loci, but most phenotypic evolution is the result of natural selection.
Most evolution (genetic change) is overall governed by genetic drift because most alleles are neutral
Most changes in allele frequencies over time have to do with genetic drift
Most evolution that affects bodies (phenotypes) is governed by natural selection
Adaptations are often compromises
most evolutionary changes and most of the variation within and between species is not caused by natural selection but by genetic drift of mutant alleles that are neutral. ... The controversy is still unsettled among evolutionary biologists.
Give two mechanisms by which harmful recessive alleles can persist in a population despite natural selection.
Harmful recessive alleles hide out in heterozygotes shielded from selection (Tay-Sachs disease)
Heterozygote advantage (sickle cell anemia)
Explain why natural selection often does not produce optimal phenotypes.
Selection can only act on living phenotypes; existing, heritable variation
Historical contingency
Selection pressures over time, partly due to chance, perfection is a moving target
Identify the typical results of sexual selection. Give two different types of sexual selection. Explain how sexual selection can lead to sexual dimorphism.
Male peacocks are colorful because of sexual selection, female peahens are not because of natural selection
Selection by females shapes male appearance
Direct competition between males for access to females
Sexual dimorphism: when the males and females look very different (deer, sheep)
Explain why phylogenetic trees are hypotheses
They are the evolutionary history of a species, a hypothesis for how we think evolution happened
Given a phylogenetic tree, be able to identify nodes, branches, common ancestors,
species, sister taxa, roots, ingroups, outgroups, clades, and orientation of the time axis
orientation of time axis: roots to tip
Define and correctly use these terms: taxon/taxa, lineage, character/trait, character transition, synapomorphy
taxon/taxa: a group of one or more populations of an organism or organisms
lineage: An evolutionary lineage is a sequence of species, that form a line of descent, each new species being the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life.
character/trait: feature of an organism (eye color) phenotype is more specific like blue/brown/green
character transition:
synapomorphy: SETS MEMBERS OF A CLADE APART FROM OTHER INDIVIDUALS
a characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants. Possession by two or more organisms of a characteristic inherited exclusively from their common ancestor.
Discuss the usefulness of topology and branch length when reading phylogenetic trees.
Given a tree, represent its topology using parenthetical notation. Be able to identify trees of different style or arrangement that share a common topology
...
Interpret a phylogenetic tree to determine the hypothesized relationship between clades or species
...
Explain what outgroups are useful for
Use an outgroup to determine which ones are derived and which are ancestral. It can show where to draw character transitions.
Understand how different types of data (morphological, DNA sequence) are used to build a phylogenetic tree
Morphological data deals with the study of the form and structure of organisms and their specific structural features. The most compelling reason to continue to collect morphological data long into the future is to resolve the phylogenetic relationships of fossil taxa and their relationships to living taxa.
Be able to identify monophyletic, paraphyletic and polyphyletic groups, and explain
how they differ. Provide a real-life example of each kind of group
monophyletic: includes the most recent common ancestor of a group of organisms, and all of its descendants. Mammalia, Aves (birds), angiosperms, insects
paraphyletic: includes the most recent common ancestor, but not all of its descendants. Traditionally defined Dinosauria, fish, gymnosperms, invertebrates, protists
polyphyletic: does not include the common ancestor of all members of the taxon. marine mammals, bipedal mammals, flying vertebrates, trees, algae
Given a tree and characters marked: Identify a shared, derived character defining a particular clade
Shared is a trait they both have
Given two trees with character transitions marked, infer which is the most parsimonious tree
the one with the fewer amount of character transitions (marks on tree) is parsimonious
Discriminate similarity between characters due to common evolutionary history (homology) and convergent evolution (homoplasy). Identify which of these traits is useful when constructing a phylogenetic tree
Homology vs Analogy (homoplasy) (convergent evolution)
Compare and contrast shared derived traits (synapomorphies) and shared ancestral traits, and discuss which are useful for building phylogenetic trees
Shared, derived characters = synapomorphies (define a clade, they tell us about phylogenetic relationships)
Ancestral is shared because of this clade and earlier ancestors have it
Explain how phylogenetic trees can be used to answer evolutionary questions. Given a phylogenetic tree, be able to interpret it to understand evolutionary relationships, patterns of evolutionary change, timing of divergence or evolutionary events, or other evolutionary questions based on a well-founded understanding of how to properly read and interpret a phylogenetic tree
...
Correctly answer the kind of questions reviewed in the Tree Thinking quiz in discussion section and explain your answers
...
Explain why this is not a paradox: An individual from any time in the human lineage could interbreed successfully with another individual in the lineage who lived 1000 years earlier. However, a modern human could not interbreed with an individual of the lineage from 5 million years ago because they are members of different species.
This is not a paradox because if an modern human tried to breed with an individual from 5 million years ago, there are genetic differences that will stop them from being able to mate.
1000 years back is the right amount of time to be able to go back and mate.
There is a point every organism reaches where they physically cannot breed with an individual from another time because they are not evolved enough/do not match up
It would be like us trying to mate with basically an ape.
Explain what a ring species is and how it is analagous to the way speciation happens over time.
Plays off above ^ A species is able to breed with another species that lives close to it geographically, and so on, which turns into a circle. Connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each
Define each of the following species concepts. For each, give an example of a kind oforganism for which they work well and a kind for which they don't apply very well.
...
Biological species concept
BBC:
A species is a group whose members have the potential to interbreed in nature and produce viable, fertile offspring. (horse + donkey = mule is not biological species concept because the mule is not fertile)
Gene flow unites
Reproductive Isolation differentiates
Some problems with the BSC:
Mating or lack of mating is hard to observe
Cannot be applied to fossils
Not applicable to asexual populations (bacteria)
Morphological species concept
MSC:
Species are defined by morphological traits alone
Used by paleontologists to define fossils
Used by others when reproductive biology is not available
Problems with MSC:
Cryptic species: species that are morphologically identical but genetically distinct
Fossil record:
Species cutoffs are somewhat arbitrary.
Ecological species concept
ESC:
Species are defined by the ecological niches they occupy.
Niches select for different adaptations, so this often overlaps with the morphological species concept.
Polar bear and grizzly bear (different niches that they occupy and different species)
Problems with ESC:
Organisms can have different niches throughout their life (newt)
List prezygotic barriers to reproduction between populations and give an example of each.
PRZB: No viable zygote is formed (usually no mating at all)
Physical isolation: physical barrier; bismuth of panama, one is in the atlantic one is in the pacific
Habitat isolation: Bus that lives in the tree roots vs on the tree
Temporal isolation: Species that breed during different time of the day, different seasons, or different years. American toad and fowlers toad
Behavioral isolation: differences in courtship behavior (lacewings)
Mechanical isolation: Mating is attempted, but morphological differences prevent its successful completion.
Gametic isolation: Sperm of one species may not be able to fertilize the eggs of another species.
List postzygotic barriers to reproduction between populations and give an example of each.
POZB: Mating occurs but offspring not viable or fertile
due to:
Reduced hybrid viability: The genes of different parent species may interact in ways that impair the hybrid's development or survival in its environment.
Fertility: When hybrids are sterile.
Breakdown: When the first hybrid is fine but when it attempts to mate, it can not produce viable, fertile offspring.
Compare and contrast allopatric vs. sympatric speciation.
Allopatric speciation is speciation that results when a population is separated by a physical barrier. It is also referred to as geographic speciation. Sympatric speciation is speciation that occurs without physical separation of members of the population.
Allopatric speciation = vicariance and dispersal
Sympatric speciation = occurs when organisms are in the same habitat, something else causes them to become different species (chloe's apple tree example) (geographically overlapping populations) habitat differentiation and polyploidy in plants
Compare and contrast vicariance vs. dispersal.
vicariance is the separation of species by a geographical barrier. eg- formation of a mtn range, or rising sea levels creat islands
dispersal - species disperses across an EXISTING barrier- eg. islands already exist - some individuals made it to the next island, underwent allopatric speciation.
Infer from a phylogeny whether a group of species arose via successive dispersals or a vicariance event. Examples: snapping shrimp, Hawaiian Drosophila.
Snapping Shrimp:
Isolation through vicariance. Lots of branches with lines
Shrimp populations became isolated by formation of Isthmus ca. 3 MYA. Isolation has allowed speciation to occur in this group
Hawaii Drosophila:
Isolation through dispersal. One branch with lines on it
Plate tectonic theory etc. allows us to age the islands. The most closely related species occur on adjacent islands, and phylogenetic branching events correspond to order of appearance of the islands
Sketch a typical phylogeny resulting from adaptive radiation.
Finches
Give one mechanism of sympatric speciation.
habitat differentiation (use habitats differently) and polyploidy in plants (Polyploidy even allows the formation of new species derived from different ancestors) Polyploids can only reproduce with other polyploids (leads to population)
Gene flow has been reduced between flies that feed on different food varieties, even though they both live in the same geographic area. (apple maggot flies and hawthorne flies)
Define half-life: A half-life is the amount of time after which half the parent isotope atoms will have decayed into the daughter isotope.
the time required for 50% of the parent to decay
Explain how measuring the amount of parent and daughter isotope tells us how long it has been since the "clock" started in that sample.
By measuring the parent and daughter isotopes, we measure the half life, which tells us how long to took for 50% of the parent to decay
Given the half-life of a radioactive isotope, you should be able to roughly estimate how much of it would be left after a given number of half-lives.
Given the half life, if it says "determine how much of this would be left after 5 half lives" so you divide by 10. If it gives you the remaining number and asks how many years it the half life, you multiply.
Explain how carbon in the atmosphere sets the carbon-14/carbon-12 ratio during an organism's lifetime.
When the organisms dies, it stops accumulating carbon, and the amount of carbon 12 in its tissues does not change over time. The carbon 14 it contains at time of death slowly decays into another element, nitrogen 14. Once we measure the ratio of carbon 14 to carbon 12, we can determine its age.
Provide the rough timescales and know what kinds of samples for which carbon-14 dating vs. uranium dating are appropriate.
75,000 million years ago is the latest for carbon-14.
238 million years ago for uranium
Even though we cannot date older fossils directly like uranium, we can use an indirect method to infer the age of fossils that are sandwiched between two layers of volcanic rock. As lava cools on a volcanic rock, radioactive isotopes from the surrounding environment become trapped in the newly formed rock. Some of the trapped radioisotopes have long half lives, allowing geologists to estimate the ages of ancient volcanic rocks. If two volcanic layers around the rock are 525 and 535 years old, the fossils are roughly 530 years old.
Identify what starts the "clock" for carbon-14 vs. uranium dating samples.
when the organism dies
When the volcanic rock hardens
Origin of life
3,900 million years ago
Origin of cells
3, 500 mya
Stromatolites: photosynthetic cyanobacteria found ~3.5 bya that persist today.
layered rocks that form when certain prokaryotes were Earth's sole inhabitants for about 1.5 billion years. These early prokaryotes transformed life by releasing oxygen to the atmosphere during the water-splitting step of photosynthesis
Cause, effect, and evidence for increasing oxygen in the atmosphere.
Cause: algae started to photo synthesize which caused the levels of oxygen to rise. 90% of life was exterminated! biggest mass extinction. Stromatolites survived. Began 2.4 billion years ago and led to the extinction of some, while proliferation of others. Eukaryotes flourished (fossil evidence and molecular clock based on DNA sequence)
Origin of Earth
46,000 mya
Based on how fit the hybrids are and how much migration there is in the parent population, predict the outcome of a hybrid zone
A hybrid zone can occur in a single band where adjacent species meet
Hybrids often have reduced fitness compared with parent species
The distribution of hybrid zones can be more complex if parent species are found in multiple habitats within the same region
When closely related species meet in a hybrid zone, there are three possible outcomes:
Strengthening of reproductive barriers (reinforcement)
Weakening of reproductive barriers (Fusion)
Continued formation of hybrid individuals (stability)
YOU MIGHT ALSO LIKE...