Unit 1 Flashcards
living organism share _ traits
5 traits
- made up of 1+ CELLS
- store and process HERITABLE INFO
- REPLICATE/REPRODUCE
- as populations, they EVOLVE
- use ENERGY
Cell Theory
- ALL organisms made of cells
- ALL cells come from pre-existing cells
- in multicellular individuals, all cells descended from a PROGENITOR CELL - the ZYGOTE
essential features of cells
- a compartment bounded by plasma membrane
- contents concentrated in an aq solution
- contains molecular info (DNA) that encodes physical attributes
- there is a boundary between them and the environment
viruses
- uses cell to replicate
- ability to store/transmit info in RNA/DNA
- non-living — can’t independently replicate/harness energy
how was cell theory tested?
REIDI’S EXPERIMENT
- two containers of meat, one open one closed
- see which one gets maggots
PASTEUR’S EXPERIMENT
- two containers of life giving broth. one open, one with swan neck (closed)
- sterilized
- open broth showed growth of life
what does this show?
Define a positive control and give an example
shows that an assumption of the experiment is true.
eg. in Louis Pasteur’s broth experiment, the open broth showed that it was capable of supporting life, supporting the experiment’s hypothesis
Define a negative control and give an example
shows what happens when a variable in an experiment is removed
eg. in Louis Pasteur’s experiment, the closed flask showed what happened when the broth was sterilized and closed.
name and describe parts of phylogenic tree
BRANCHES: populations throughout time
NODES: occur when ancestral group splits. more than two groups is a POLYTOMY
TIPS (TERMINAL NODES): groups living today or dead ends
define taxon
- Any named group of organisms. can be a single species (Homo sapiens) or a large group of species (primates).
- Tips connected by a single node on a tree are called sister taxa.
define monophyletic group and an outgroup
MONOPHYLETIC: A group consisting of
an ancestral species and all of its descendants.
OUTGROUP: outlying popultaion in a monophyletic group. has no other nodes.
exception to the validity of cell theory
LUCA (last universal common ancestor) because we don’t know where it originated
exception to cell theory
LUCA because we don’t know if it had any ancestors. therefore we can not confirm that all cells come from other cells
NS acts on ____
evolution acts on ___
NS acts on INDIVIDUALS
evolution acts on POPULATIONS
key ingredients of NS
1) VARIATION that is
2) HERITABLE and
3) INFLUENCES FITNESS
why do cells exist?
- CONCENTRATE REAGENTS for biological reactions
- make CHEMICAL GRADIENTS possible across plasma membrane that can store energy
- link a PHENOTYPE to the same physical space as the
genotype that encodes it
define adaptation and characteristic
- a characteristic influences fitness
of an individual in a certain environment (not all characteristics are adaptations) - adaptation is the process of a species acquiring fitness-improving traits over time
central dogma of molecular biology
- relationship between DNA, RNA and proteins (how one converts to another)
- how information flows in biological systems.
define speciation
- when populations, usually evolving in isolation for some period of time, accumulate genetic differences that causes reproductive incompatibilities
between them. - molecular variation in DNA/RNA helps us understand (nucleotides similar in closely related, less similar in less related)
causes of speciation
- GENETIC
- ECOLOGICAL
- BEHVIOURAL
domains of tree of life. how are they related.
- BACTERIA
- ARCHEA
(both prokaryotes, lack nucleus) - EUKARYA (animals, fungi)
- A and E connect to same branch
list of taxonomic classifications
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus (italics)
- species (italics, lower case)
artificial selection
- NS where humans drive course of evolution
- repeated = changes in domestic pop over time
unintended consequences of artificial selection
- population problems (ex only hunting large sheep, cod fishing = smaller cod)
- in general, small size, early maturation and behavioural responses
evidence for evolutionary change over time
- FOSSILS
- EXTINCTION
- ancient DNA
- TRANSITIONAL FORMS (ex limb development/loss, gaining upright posture)
- VESTIGIAL TRAITS (ex goosebumps)
- SPECIATION and ARTIFICIAL SELECTION can be observed now
(ex herbicide resistance) - GEOGRAPHIC CONTINUITY (extinct fossil species succeeded by similar living in same region)
- GEOGRAPHIC RELATIONSHIPS: close relations of living species across different locations
- HOMOLOGY (genetic, developmental,
structural)
homology: genetic and developmental
a similarity that exists in species that was inherited from an ancestor
GENETIC: similarity among species in DNA sequences, gene content, or other genetic attributes that is due to shared ancestry
DEVELOPMENTAL: similarity among species
in embryonic traits that is due to shared ancestry
why does homology matter?
- toxins and allergies may similarly affect closely related species
- medicines can be tested in other species
- Biological function in humans can be inferred from homologous function in other species
4 processes that drive evolution/change allele frequency
1) NATURAL SELECTION
2) GENETIC DRIFT
3) GENE FLOW (migration)
4) MUTATION
theory of evolution
a) species are related to each other
b) species can change through time
fitness
ability of an individual to produce
offspring as compared to other individuals of the same
species
define evolution
a change in allele frequency in a population over time
polymorphic
A species that has two or more distinct phenotypes in the same interbreeding population at the same time
ex. 2 different strains of tuberculosis, one is antibiotic resistant one is not
morphology
The overall shape and appearance of an organism and its component parts.
in situ hybridization
Technique for detecting specific DNAs and mRNAs in cells and tissues by use of labelled complementary probes.
Can be used to determine where and when particular genes are expressed in embryos.
myths about evolution
- not goal/want/need directed
- no hierarchy of life
- no altruism
- doesn’t result in most optimal phenotype
Why doesn’t natural selection result in
the most optimal phenotype?
- Genetic Correlation: fitness trade-off
- Historical Constraints: Present variation biases future possibilities
- Formal Constraints: can’t defy laws of physics
- Temporal Constraints: evolution occurs by mutation and may take a long time to happen
gene flow
causes change in allele freq. through migration
genetic drift
causes change in allele freq. randomly generation to generation
purpose of hardy-weinberg principle
to create a null hypothesis to help better understand what mechanisms of evolution are influencing a population
heterozygote advantage
- A pattern of natural selection that favours heterozygous individuals
- Tends to maintain genetic variation in a population and thus is a form of balancing selection.
directional selection
- mode of NS that changes the average value of a trait (shifts it more towards a favourable characteristic)
- reduction in genetic diversity
stabilizing selection
mode of NS that favours phenotypes near the middle of the range of phenotypic variation.
- Reduces genetic variation in a population
types of natural selection
- balancing selection (no allele favoured)
- directional selection
- stabilizing selection
- disruptive selection
- frequency dependant selection (neg and pos)
disruptive selection
-mode of NS that maintains or increases amount of variation in a trait (double bell curve)
negative frequency dependant selection
fitness highest in rare phenotypes
positive frequency dependant selection
fitness highest in common phenotypes
genetic drift
- any change in allele freq. in a population due to CHANCE
- not adaptive changes
- can lead to stochastic loss/fixation: genetic variance in pop declines
- more prominent in small populations
fixation vs extinction
caused by genetic drift
Fixation: only one allele survives
other allele is extinct
causes of genetic drift
random even or process that involves sampling of allele from one gen to the next
eg. founder effect and bottlenecks
how does founder effect cause genetic drift
population isolation causes decreased alleleic variation
how do bottlenecks cause genetic drift
SEVERITY + DURATION impact strength of bottleneck in decreasing allelic variation
gene flow
migration
movement of alleles from one pop to another.
homogenizes allele frequencies across populations
nonrandom mating
biased mating
examples: inbreeding, sexual selection
inbreeding
- increases frequency of homozygotes (homozygosity) and reduces frequency of heterozygotes in each generation
does NOT change allele frequency, DOES change genotype frequency
inbreeding depression, causes
- decline in fitness from increasing homozygosity and decreasing heterozygosity
causes:
1) many harmful mutations are recessive
2) heterozygote advantage
** DOES change allele frequencies because
1) harmful homozygous recessives more common
2) beneficial heterozygous genotypes less common
these two things make individuals less fit, therefore NS acts on allele frequencies
red queen hypothesis
species must constantly evolve to avoid extinction as a consequence of being outcompeted by
other evolving competitors.
why sex?
asexual reproduction will win over sexual every time BUT…
- males can help out with ‘parenting’
- male competition: better genes, less mutations
- genetic recombination benefit to offspring
genetic recombination
- natural selection ‘placing’ good and bad mutations together in order to maximize fitness
isogamous species
all individuals produce the same gametes (ex yeast)
how does sexual selection violate HWE
by causing certain alleles to increase or decrease in frequency, resulting in evolutionary change.
consequences of sexual selection
sexually dimorphic traits
sexual conflict (traits that are advantageous in one sex but harmful in another)
pros and cons of sexual reproduction
PROS
- male parental care
- SS removes bad alleles
recombination
CONS
- have to make males (2 fold cost of sex)
- may disrupt advantageous combinations of alleles
- can be risky (std, predation)
causes of sexual selection
female choice
- honest advertising
- nuptial gifts
male male competition
sensory exploitation
evidence for sexual selection in males
variation in reproductive success high in males, low in females.
more females have offspring, only few males have many.
mechanisms of reproductive isolation
Prezygotic isolation
- temporal
- habitat
- behavioural
- gametic barrier
- mechanical
postzygotic isolation
- hybrid viability (embryos don’t develop properly)
- hybrid sterility (sterile offspring)
