ISCI 1A24 - Lifesci Midterm Review (Fall)

how do scientists "know"?

through observation and process

how do scientists mitigate uncertainty about what they know?

replication/replicating the process

observation

(raw) information obtained through the senses, without bias

categorizations

(biased) analysis of observations to make conclusions (i.e. grouping things based on shared properties), arbitrary and biased based on human experience

what are the principle determinants if something is alive?

1. it has DNA (RNA)

2. it can evolve

3. it can grow and reproduce

why is a virus non-living?

they need a host to reproduce, they don't grow, they can't make their own energy, it is not made of cells, etc.

why is bacteria living?

it has DNA, it is made of cells, it can make its own energy, it can evolve, and it can grow and reproduce in the right environment

what are the main taxonomic categories for living organisms?

domain, kingdom, phylum, class, order, family, genus, species (kids play catch over farmers green shed)

how are organisms placed into taxonomic categories?

dichotomous keys (also could use cladograms and phylogenies, which take time into account)

what is bias?

showing preference towards toward a particular viewpoint

how has human bias been exhibited in the categorization of living things?

focus on vertebrates though invertebrates are 97% of the population, anthropocentrisim, taxonomic inertia

anthropocentrisim

humans have a tendency to categorize and prioritize organisms based on their utility or relevance (economic or cultural importance) to human interests. this bias has led to the overemphasis on certain species while neglecting others (e.g. monera, the original classification which contained ALL of archaeabacteria and eubacteria)

dichotomous key

dichotomous keys are systematic tools used to categorize and identify organisms and objects through a series of yes/no questions or statements

how are dichotomous keys useful?

they provide a consistent and efficient way to determine classifications, aiding species identification and quality control

how are dichotomous keys biased?

subjective criteria, simplification, incomplete information

identify different ways to organize biological systems

population, physiological, community, landscape, ecosystem, evolutionary

taxonomy

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

phylogenetics

studying the evolutionary history and relationships between species, relating organisms back to their common ancestors

why is studying biological systems from multiple perspectives more appropriate?

it allows us to more accurately understand and classify organisms when we consider that there are many factors that contribute to how an organism is defined; that one perspective isn't necessarily more important than another, therefore it is important to consider that there are perspectives which are not being considered, though they may be equally as contributive to how a species is defined

is this realistic?

not necessarily - it is impossible to consider all perspectives, which then creates the difficulty of deciding which perspectives to consider, which ones we don't know about, etc. it also makes it much more difficult to organize a system if there is much more to consider. however, it is always beneficial to our knowledge to study from multiple perspectives.

why are hierarchical arrangements of organization (for biological systems) erroneous?

they only consider one perspective in their classification, creating a situation where important characteristics are overlooked to adhere to the criteria that have been previously created for this organization

what are the components/sections of a scientific study?

substantiate, argue, support

what is diversity?

comparing and contrasting two or more entities (organisms, environments, etc); diversity is a tool used for comparison, therefore it is a relative term

how is diversity measured?

through comparisons; quantitatively, through indices (e.g. Shannon Index, Simpson Index)

what are the types of diversity?

alpha, beta, gamma

what is alpha diversity?

local; diversity within one community/area/ecosystem

beta diversity

differential; diversity BETWEEN sampling units or sites i.e. comparative (e.g. one quadrant vs. another quadrant)

gamma diversity

regional; diversity over a wide range of communities or habitats (i.e. similar to alpha but across a large spatial scale)

what is species richness (s)?

the number of species (or genotypes or habitats) in a community

what is species evenness?

relative abundance of each species, i.e. comparing the number of the population of each species; proportional diversity which gives us insight into the actual diversity of the area

what is a bioindicator species?

a species or group of species whose population fluctuate in space and/or time based upon measurable changes in the environment (e.g. grass); this can also be a gene (biomarkers) or a habitat (e.g. Great Barrier Reef)

why are bioindicator species useful?

a change in the abundance of the species provides a window into (environment) change

what characteristics identify a good bioindicator species?

common, easily identifiable, and easily influenced characteristics which can be used to reenforce and substantiate that change has happened

how is diversity linked to biological organization/the complexity of life?

comparison! diversity is based on comparison/is a tool for comparison, and something must be classified before it can be compared and be defined as diverse. however, for something to be classified, it first has to be compared to something else. and so the complex cycle (of life) continues!

explain the statement "science is a process"

science is a process because it is continually changing, new information is always being tested and supported, which means that previous scientific theories are always being challenged, and are therefore growing; this is the whole point of science, that we are continually learning and changing and developing new ideas so that we may better explain the phenomena which we observe

historical example of "science is a process"

evolution; Plato, Aristotle, Anaximander, Empedocles, and eventually Lamarck - originally we thought that individuals changed/evolved, and those characteristics were passed on (inheritance) - now we know that evolution is a population based event, which is supported by the theory of natural selection

what is the most important scientific contribution of Darwin and Wallace?

"descent with modification" through natural selection and gradualism (i.e. mechanisms of evolution); that populations changed over periods of time by being selected for by their environment; all species descended from now extinct species

what are the two main points generated from the origin of species?

1. evidence that all organisms are descendants of different and now extinct ancestral species

2. that natural selection is the mechanism for evolution

what are the modern postulates of the "Theory of Evolution by Natural Selection"?

1. populations evolve

2. traits are heritable

3. evolution by natural selection is not progressive

when has natural selection occurred?

when individuals with certain alleles have increased fitness

what is evidence of natural selection?

vestigial characters, homologous characters, fossils

vestigial characters

characters that served a function in ancestors but no longer do so

homologous characters

characters in different organisms that are similar because they were inherited from a common ancestor that also had that character, but are not necessarily currently used for the same thing

population evolve

their evolution is defined as changes in allele frequencies over time

traits are heritable

adaptations are genetically based traits that increases an individual's fitness in a particular environment. (so adaptations are heritable)

evolution by natural selection is not progressive

organisms do not do things for the good of the species, and not all traits are adaptive. all adaptations are constrained by trade-offs as well as genetic and historical factors

are all adaptations beneficial?

organisms do not do things for the good of the species, and not all traits are adaptive. all adaptations are constrained by trade-offs as well as genetic and historical factors

evolution as a fact

we can make observations of changes in gene frequencies in a population across generations, this is something we can literally see happen, therefore it is a fact

evolution as a theory

the mechanisms as to which evolution occurs, (i.e. natural selection) are theories because we cannot literally observe it happening, so we cannot prove it is happening. we simply have evidence to support that it does.

why is the study of evolution an integrated science?

because it relies on observation, and considering multiple perspectives and drawing from multiple scientific disciplines instead of just one in order to explain the complex mechanisms and processes of life on Earth (Darwin was an integrated scientist!). there are so many factors which play into evolution, not simply biological, therefore integrating multiple disciplines is essential for a more accurate concept of evolution.

what is a species?

group of organisms that can interbreed and produce fertile offspring

what is the biological species concept?

species are groups of interbreeding natural populations that are reproductively isolated from other such groups

what are the four main mechanisms leading to evolution?

natural selection, genetic drift, gene flow, and mutation

what is natural selection?

the process whereby organisms better adapted to their environment tend to survive and produce more offspring; occurs through directional selection, divergent selection, sexual selection, and artificial selection

directional selection

an increase in the frequency of one allele (reduces genetic diversity in a single direction); mean is shifted (e.g. cliff swallows)

divergent selection

selection against intermediate phenotypes; reduces genetic diversity in two or more directions; can lead to speciation through adaptive radiation (e.g. Galapagos finches)

adaptive radiation

evolution from a common ancestor of many species adapted to diverse environments (i.e. they split!)

sexual selection

selection for sex-specific traits that increase individual fitness; usually reduces genetic diversity in one direction per sex (therefore is directional), occurring through mate choice/functional ecology (big guy, little girl) OR can increase genetic diversity (therefore is divergent) through sexual strategy (sunfish!)

artificial selection

selection for specific traits that are desired for a species (typically human) purpose; the species is being a selective pressure for another species; can both reduce(usually) or increase genetic diversity (e.g. pigeons!)

genetic drift

a change in the allele frequency of a population as a result of some random pressure rather than natural selection; it is not adaptive, can lead to the loss of alleles, and is more significant in smaller populations (e.g. bottleneck effect)

gene flow

movement of alleles from one population to another by immigration and emigration, equalizing gene frequencies bwtn source and recipient populations; random, but tends to reduce genetic differences btwn populations

mutation

a random error in gene replication that leads to a change, restores genetic diversity by creating new alleles; usually bad (deleterious alleles which lower fitness), but can also give beneficial alleles; slow acting but significant in organisms with short generation time (e.g. bacteria)

why is artificial selection natural selection?

because it is a response to a selective pressure which increases fitness accordingly. though we are the ones deciding that pressure and therefore what is considered increased fitness, the population itself is still adapting to the pressure and therefore natural selection is occurring (are humans natural?)

why is genetic drift an important issue concerning the conservation of species?

genetic drift generally decreases genetic diversity, thereby decreasing fitness and affecting the species ability to survive in a given environment

what are the two mechanisms of speciation?

allopatric speciation and sympatric speciation (also parapatry!)

allopatry

gene flow is decreased because populations are geographically separated; in context of evolution, the two populations adapt separately to their respective environments, and eventually evolve into different species

parapatry (parapatric speciation)

condition in which two or more populations live in the same geographic area, or close enough to permit interbreeding; in context of evolution, the two species interbreed enough that a third species adapts and evolves separately from the original two

what is a result of parapatric speciation?

hybrid depression; decrease in gene flow

sympatry

speciation occurring within one parent population remaining in one location where a mutation or some event occurs such that a new species is created; in the context of evolution, a new species evolves amongst the original one to adapt to this event/mutation (through natural selection)

genotype

genetic makeup (alleles) of an organism

phenotype

physical characteristics/traits of an organism

why is the hardy-weinberg principle considered a null hypothesis?

because if it holds true, that means that evolution has not occurred, therefore if we are trying to prove that evolution has occurred in a species, if the null hypothesis is true then our hypothesis is not supported

differentiate homozygous and heterzygous genotypes

a homozygous genotype is a genotype where the alleles are the same (therefore either both are dominant or both are recessive), while a heterozygous genotype is a genotype where one allele is dominant and the other is recessive

what can be said about evolution?

populations evolve, individuals do not

what can be said about adaptation?

it is an individual mutation