Exam 1 Flashcards
Can natural selection fashion the perfect organism?
no, it only selects on existing variations within a population. Therefore, as the environment is under the influence of the elements it is an everchanging and the organisms which inhabit must change with it to avoid extinction
Diploidy
a cell containing two sets of chromosomes (2n), one set inherited from each parent
What are Darwin’s two observations?
Darwin’s two observations are (1) members of a population vary greatly in their inherited traits and (2) all species can produce more offspring than the environment can support, many of these offspring fail to survive and reproduce.
Correlational relationship
relationships between two events or actions, however this does not mean that one event simply causes another event to occur.
Cause and effect relationship
one event/variable causes an outcome from the other event/variable to occur.`
Which is more rigorous a cause & effect or correlational relationship?
cause-and-effect relationship is more rigorous than a correlation between two variables because a cause-and-effect relationship must be established.
Evolutionary biology
study of evolution, or the study of the process by which species accumulate differences from their ancestors as they adapt to different environments over time.
Father of evolution
Charles Darwin
Natural selection
a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Define gene frequency
the percentage of a population that carries allele at a particular locus
Who is Jean-Baptiste De Lamarck and what contributions did they make regarding the development of evolutionary theory?
developed two principles: (1) use and disuse of parts-the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate. and (2) the inheritance of acquired characteristics-stated that an organism could pass these modifications to its offspring.
Who is Carolus Linnaeus and what contributions did they make regarding the development of evolutionary theory?
developed the binomial naming system for species according to genus and species, which classified species into increasingly complex categories.
Who is James Hutton and what contributions did they make regarding the development of evolutionary theory?
proposed the theory of gradualism-profound geological changes took place through a cumulative effect of slow but continuous processes identical to those currently operating.
Who is Alfred Russel Wallace and what contributions did they make regarding the development of evolutionary theory?
developed and published a theory of natural selection nearly identical to that of Darwin’s, just earlier.
What are the various lines of evidence that support evolutionary change caused by natural selection?
- Although natural selection occurs through interactions between individual organisms and their environment, individuals do not evolve. A population is the smallest group that can evolve over time.
- Natural selection can only act on heritable traits that are passed from organisms to their offspring. Characteristics acquired by an organism during its lifetime may enhance its survival and reproductive success, but there is no evidence that such characteristics can be inherited by offspring.
- Environmental factors vary from place to place and from time to time. A trait that is favorable in one environment may be useless or even detrimental in another environment.
What are the four main mechanisms that contribute to evolutionary change?
(1) homology
(2) fossil record
(3) biogeography
(4) natural selection
Phylogenetic tree
a diagram that represents evolutionary relationships among organisms; they are hypotheses not facts.
Cladogram
diagram that shows the evolutionary relationships among a group of organisms
Significance of nodes in phylogenetic trees and cladograms
represent divergences or speciation events.
What did biogeography contribute to the theory of evolution?
we can use our understanding of evolution and continental drift to predict where fossils of different groups of organisms might be found.
Biogeography
the scientific study to the geographic distribution of species
What did paleontology contribute to the theory of evolution?
fossils show the evolutionary changes that have occurred in various groups of organisms.
Paleontology
the study of extinct species via fossil evidence
What did relative dating contribute to the theory of evolution?
fossils buried in the lower layers are older than those encased in the upper strata, which were formed more recently
Relative dating
method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
What did the law of superposition contribute to the theory of evolution?
within a sequence of layers of sedimentary rock, the oldest layer is at the base and the layers get progressively younger with ascending order in the sequence.
What did radiometric dating contribute to the theory of evolution?
fossils buried in the lower layers are older than those encased in the upper strata, which were formed by more recent deposits.
What did continental drift contribute to the theory of evolution?
movements in the mantle cause the plates to move over time, shifting the continents and the species which inhabit them
A naturally occurring isotope (potassium-40) has a half-life of 1.3 billion years. The original parent isotope weighed 12 mg. The amount of original parent isotope left is 3 grams. What is the age of the rock?
Half-life-the amount of time in which the radioactivity of a radioisotope decreases to half of its original value. Therefore if the original parent isotope weighed 12 mg, after 1.3 billion years, the amount of potassium-40 left would be 6 mg and after another 1.3 billion years later, it would be 3 mg. Therefore, the age of the rock would be 2.6 billion years.
Binomial nomenclature
instituted by Carolus Linnaeus to avoid ambiguity when communicating about research. The first part of the name refers to a species genus to which the species belongs. The second part, called the specific epithet, is unique for each species within the genus.
Classification hierarchy (from species up to Kingdom)
(“King Phillip Came Over For Good Spaghetti”)
The classification of the hierarchy is as follows:
(1) species
(2) genus
(3) family
(4) order
(5) class
(6) phylum
(7) kingdom
Population
a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
Gene pool
the aggregate of all copies of every type of allele at all loci in every individual in a population
Polyploidy
a chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division
Homozygous
having two identical alleles for a given gene
Heterozygous
having two different alleles for a given gene
Allele frequency
how common an allele is in a population
Hardy-Weinberg equilibrium
the state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.
Why is Hardy-Weinberg equilibrium useful?
can be used to predict genotype and allele frequencies in future generations
What are the assumptions of the Hardy-Weinberg equilibrium?
- No mutations
- Random mating
- No natural selection
- Extremely large population size
- No gene flow
Founder effect
when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population
Bottleneck
when a severe drop in a population occurs, the population has passed through a “bottleneck” that greatly reduces its size
`Describe how the bottleneck effect applies to the Illinois prairie chicken
As prairies were converted to farmland during the 1800s and 1900s, the number of greater prairie chickens plummeted. The few surviving birds had low levels of genetic variation, and less than 50% of their eggs hatched, compared with much higher hatching rates of the larger populations in Kansas and Nebraska that did not experience events of bottlenecking.
Darwinian fitness
the capacity of a variant type to invade and displace the resident population in competition for available resources
Directional selection
occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population’s frequency curve for the phenotypic character in one direction or the other
Disruptive selection
when individuals with extreme phenotypes (or genotypes) within a population have a fitness advantage over intermediate individuals
Stabilizing selection
when genetic diversity decreases, favoring an intermediate trait or genotype
Species
a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not produce viable, fertile offspring with members of other such groups
How long do typically ‘successful’ species exist?
Successful species exist for millions of years on average.
What are pre-zygotic barriers that prevent different species from crossbreeding.
(“before the zygote”) block fertilization from occurring. Such barriers typically act in one of three ways:
(1) by impeding members of different species from attempting to mate
(2) by preventing an attempted mating from being completed successfully
(3) by hindering fertilization if mating is completed successfully
What are post-zygotic barriers that prevent different species from crossbreeding.
(“after the zygote”) may contribute to reproductive isolation after the hybrid zygote is formed.
(1) Developmental errors may reduce survival among hybrid embryos.
(2) Problems after birth may cause hybrids to be infertile or decrease their chance of surviving long enough to reproduce.
Allopatric speciation
gene flow is interrupted when a population is divided into geographically isolated subpopulations
Examples of allotropic speciation
(1) the water level in a lake may subside, resulting in two or more smaller lakes that are now home to separated populations
(2) a river may change course and divide a population of animals that cannot cross it
Sympatric speciation
speciation occurs in populations that live in the same geographic area
Examples of sympatric speciation
can occur if gene flow is reduced by such factors as polyploidy, sexual selection, and habitat differentiation.
What population characteristics must be considered when discussing isolation mechanisms?
Morphological species concept and the Ecological species concept
Species isolation
the existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring.
What defines the boundaries between Eras, Periods and Epochs?
(1) Era’s (composed of the Paleozoic Era, Mesozoic Era, and the Cenozoic Era, with mass extinctions marking the boundaries between eras)
(2) Period’s (the subdivisions of each of the Era’s mentioned above)
(3) Epoch’s (a distinct period of geological time).
Geological time scale
is a standard time scale dividing Earth’s history into time periods
Molecular clock
a method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes evolve at constant rates.
What is the advantage of combining a molecular clock with a ‘standard’ cladogram?
a standard clock allows evolutionary distances to be objectively measured.
Parsimony
the principle that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts
Adaptive radiation
period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities
Examples of adaptive radiation
the Galápagos finches are thought to have descended from an ancestral finch species that reached the archipelago from South America or the Caribbean. Over time, the Galápagos finches diversified from their ancestor as populations became adapted to different food sources on their islands
What causes adaptive radiation?
(1) mass extinction of species, with the goal of filling the ecological roles once occupied by the now extinct species
(2) organisms that arise in an adaptive radiation can serve as a new source of food for still other organisms.
(3) initiated when a few organisms make their way to a new, often distant location in which they face relatively little competition from other organisms
Convergent evolution
the evolution of similar features in independent evolutionary lineages
Examples of convergent evolution
the flying squirrel and the sugar glider, shark and dolphin bodies, etc.
Phylogeny
the evolutionary history of a species or group of species
What tools do we use to reconstruct phylogenetic relationships?
systematics, a discipline focused on classifying organisms and determining their evolutionary relationships
What are the key requirements that need to be considered when hypothesizing about the origin of life?
(1) the ability to reproduce, evolve, move, metabolize/process energy, and grow
(2) has a need for water
(3) contains DNA
(4) can die/recycle its nutrients
(5) contains order/cell structure/hierarchy
What led to the rapid increase in atmospheric O2? When did this occur and what did it allow for?
Most atmospheric oxygen gas (O2) was produced because of the water-splitting step of photosynthesis. The free O2 likely dissolved in the surrounding water until it reached a high enough concentration to react with the elements dissolved in water. This would have caused the oxidation of iron and subsequently the formation of iron ore, until all the dissolved iron was precipitated. Then the remaining O2 would have gassed out and entered the atmosphere after all the seas and lakes had become saturated with O2.
Serial endosymbiosis
proposes that mitochondria evolved before plastids through a sequence of endosymbiotic events. Explains the origin of nucleated eukaryotic cells by a merging of archaebacterial and eubacterial cells.
Advantages of multicellularity in the Eukaryotes
- ability to carry out complex metabolic reactions
- ability to adapt to new environments
- ability to grow larger
- ability to increase complexity
Briefly describe the causes and consequences of the 6 major extinctions on Earth.
Five mass extinctions are documented in the fossil record over the past 500 million years. These events are particularly well documented for the decimation of hard-bodied animals that lived in shallow seas, the organisms for which the fossil record is most complete. In each mass extinction, 50% or more of marine species became extinct.
The sixth major extinction could be due to the actions of humans destroying habitats and causing global warming, therefore destroying species by the millions.
How do we explain biological/physiological complexity? In other words as a scientist, how would YOU respond to the argument of irreducible complexity?
Novel properties arise at each successive level of biological complexity because of the arrangement of building blocks at the underlying level. Therefore, each level of complexity is due to the addition of a feature or structure on a prior level. Therefore, reducible complexity is a phenomenon that cannot occur, due to natural selection leading to the survival and reproduction of individuals who inherit traits that allow for this process.
Monophyletic groups
pertaining to a group of species that consists of a common ancestor and all its descendants
Paraphyletic groups
pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants
Polyphyletic groups
pertains to organisms that are grouped together despite not being closely related to one another
An example of a polyphyletic group is bats and birds: both have wings, but they have evolved separately.
What do branching lengths represent in a cladogram?
show the time or quality of divergence
How are a cladograms branching length values calibrated or calculated?
the difference between height of lower node and height of upper node
Three main domains of life
(1) Archaea
(2) Bacteria
(3) Eukarya
Role of horizontal gene transfer
transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.
“Ring of life” (conceptual model)
theorizes that Archaea, Bacteria, and Eukarya domains originated from a pool of primitive prokaryotes
