post midterm Flashcards
what is micro evolution
a change in the genetic makeup of a population from one generation to the next
macro evolution
the evolution of taxa above the species level (genus, family, order) large scale structures
phenotypic variation
heritable variation in appearance and/or function
phenotypic variation in garden snails
shells of garden snails vary considerably in appearance
bahaman land snails phenotypic variation
shells of land snails from a population in the bahamas look very similar
quantitative variation
individuals differ in small ways ex. variation in the number of hairs on their head (bar or curve graph)
qualitative variation
characteristics with discrete states
ex. snow geese are either blue or white and associate with other of the same colour
polymorphism
discrete variants of character ex. the background colour, number of stripes and colour of stripes or human blood types
(calculate frequency)
ways phenotypic variation within populations can be caused?
- genetic differences
- environmental factors
- interactions between genetics and the environment
environmental effects on phenotype in hydrangea macrophylla
in acidic soil produces blue flowers
in neutral soil produces bright pink flowers
what is an allele?
a variation of the same sequence of nucleotides at the same place on a long DNA molecule
what is a locus ?
location of a gene on a chromosome
what is a gene pool?
all alleles at all loci in a population (the set of all genes or genetic info)
4 distinct processes that cause evolution?
- mutation
- genetic drift
- gene flow
- natural selection
why does genetic variation exist in a population?
individuals possess different versions of the same gene (different alleles)
what is gene flow?
alleles and genotypes of a population can change due to migration into or out of the population
ex. young male baboons move from one population to another after experiencing aggressive behaviours by older males
where is gene flow most common?
in plant populations where pollen carrying wind or seed carrying animals
ex. blue jays are agents of gene flow for oaks when the birds carry acorns to new populations
genetic drift?
random changes in allele frequencies, important in smaller populations, reduces genetic variability
founder effect?
due to few individuals starting new populations because they carry only a sample of their parents populations genetic variation
population bottle neck?
reduction in alleles due to population reduction (decrease in size of the gene pool)
decrease in genetic diversity and loss of rare alleles
factors such as disease, starvation, and hunting may kill a large part of the population
what’s is mutation?
- change to the double strand sequence of DNA
- spontaneous heritable variation in DNA
- rare event significant over longer time scales
- caused by radiation, hazardous chemical, environmental factors
what is natural selection?
favours some combinations of traits over other resulting in differential survivorship and reproduction
Ernst Mayer defined biological species
- if the members of 2 populations interbreed and produce viable fertile offspring under natural conditions they belong to the same species
- their fertile offspring will produce the next generation of that species
- this explains why individuals if a species look alike
what mechanisms produce distinct species?
- microevolutionary processes alter the pattern and extent of genetic and phenotypic variation with populations
- when these processes differ between populations the populations will diverge genetically
- they may become so different that we recognize them as distinct species
what do reproductive isolating mechanisms do?
prevent individuals of different species from mating and producing successful offspring, prevent gene pools of distinct species from mixing
what are prezygotic mechanisms?
occur before zygote formation
include:
- ecological isolation from habitats
- temporal isolation from mating timing
- behavioural isolation from mating signals, sexual selection
- mechanical isolation from reproductive structures
- gametic isolation from gamete incompatibility
examples of ecological isolation?
- 2 species in different habitats in the same area may encounter each other
even though they are not isolated by obvious geographical barriers (northwestern garter snake and ribbon snake)
example of temporal isolation?
- species that their geographic range might overlap but they breed during different times/seasons cannot mix their gametes
(western spotted skunk and eastern spotted skunk)
example of behavioural isolation?
there is little or no sexual attraction between males and females of different species due to differences in behaviour of physiology
(blue footed boobies and red footed boobies)
what is mechanical isolation? and example
mating is attempted but morphological differences prevent its successful completion
ex. Bradybaena approach each other headfirst when they attempt to mate once their heads move past each other the genitals emerge, if the shells spiral in the same direction mating can occur otherwise the snails genitals will not align
what is gametic isolation?
it is difficult for gametes if different species to fuse because proteins on the surface of the eggs and sperm bind poorly to each other
ex. sea urchins
what are postzygotic isolating mechanisms?
prevent the development of fertile adults, inter species offspring are reproductively isolated if they are less fit than intraspecies offspring
- reduced hybrid inviability (species hybrids don’t survive
- reduced hybrid fertility (species hybrids do not produce functional gametes
- hybrid breakdown (F2 exhibits reduced survival or fertility
what is reduced hybrid inviability?
hybrid zygotes fail to reach sexual maturity ex. salamanders
what is reduced hybrid fertility?
hybrids fail to produce functional gametes ex. donkey + horse = mule
what is hybrid breakdown?
some first generation hybrids are viable and fertile but when they mate offspring of the next generation are feeble or sterile ex. strains of cultivated rice
what is speciation?
- the process leading to the formation of new species, also the source of biological diversity
- species of sexually reproducing organisms arise via reproductive isolation
how does geographic isolation promote allopatric speciation?
birds and other organisms that easily disperse across canyon have not diverged into different species on opposite side of the canyon
what is adaptive radiation on an island chain?
- ecological opportunities exist, may stimulate evolutionary changes
- water barrie’s restrict gene flow between populations so populations on different islands may evolve adaptations to their local environments
what is sympatric (same country) speciation?
- speciation occurs in populations that live in the same geographic area
- less common than allopatric speciation
- factors like polyploidy can promote allopatric speciation — a species may originate from an accident during cell division that results in extra sets of chromosomes
when did the planet form?
4.6 billion years ago
when did the chemical signatures of life date back to?
3.8 billion years ago
when were the first prokaryotes?
3.5 billion years ago
when did the first eukaryotes appear?
1.8 billion years ago
why was original earth inhospitable?
- the surface was molten lava
- it was bombarded by meteors and lightning
- volcanoes released gases (N2, CO2, water vapour, helium, methane, ammonia, hydrogen) NO O2
- too hot to form seas and lakes
what is a deinococcus radiodurans?
an extreme species, the toughest known bacterium, and can survive cold, dehydration, vacuum, and acid
known as a polyextremophile
what is an example of a bacteria living in the human body?
staphylococcus epidermidis
what condition on the original earth made the origin of life possible?
- the no living synthesis of small organic molecules (amino acids, DNA - adenine, thymine, cytosine, and guanine, in RNA the thymine is replaced by uracil
- the joining of these molecules into macromolecules (protein and nucleic acids)
- the packaging of these molecules into protocells
- the origin of self-replicating molecules that made inheritance possible
why were meteorites important to early earth?
they are a source of organic molecules that contain more than 80 amino acids, as well as lipids, simple sugars, and uracil
what was the first genetic material and why?
RNA
- plays a central role in protein synthesis and can function as an enzyme-like catalyst
- have shapes that enable them to replicate faster with fewer errors
- able to replicate and store genetic i for about the vesicles that carried them
once RNA sequences that carried genetic info appeared in protocells what changes would have been made possible?
- RNA could have provided the template on which DNA nucleotides were assembled
- double stranded DNA is a more chemically stable responsible for genetic info
- DNA can also replicate more accurately
- once DNA appeared the stage was set for blossoming new forms of life
what are the oldest fossils and how old are they?
- stromatolites (layered rocks that form from the activities of certain prokaryotes)
- 3.5 billion years old
why are proteins the dominant structural and functional macromolecules?
greater diversity, higher rate of catalysis, DNA is more structurally complex and stable than RNA which is better for storing genetic info
how is protein made?
info is stored in DNA — info in DNA is copied into RNA — info in RNA guides the productions of proteins
what are the first 3 eons in geologic record?
hadean, archaean, and proterozoic
what eras are in the phanerozoic eon?
paleozoic, mesozoic, and cenozoic
what were earths first organisms ?
prokaryotes (anaerobic chemoheterotrophs) that lived in the ocean
where did photosynthesis first evolve?
in photosynthetic prokaryotes similar to cyanobacteria (2.7 billion years ago)
what do eukaryotes have that prokaryotes don’t?
nuclear envelope, mitochondria, ER, other internal structures
what does the mitochondria do?
requires oxygen from breathing for cellular respiration to occur
what is cellular respiration?
the process where energy rich food molecules (sugars, fats, and other fuels) are broken down to water and carbon dioxide and the energy is captured in ATP
what are chloroplasts ?
- yellow green plastids where
- photosynthesis occurs in plant cells
they are surrounded by outer and inner boundary membranes that completely enclose the inner compartment (the stroma) - within the storms is the thylakoids (sacs) that contain chlorophyll, a green pigment that absorbs light energy and converts it to chemical energy in photosynthesis
what is the rough ER?
- many ribosomes in outer surface
- proteins made on ribosomes attached to the ER enter the ER lumen where they fold into their final form
what is the smooth ER?
- no ribosomes on surface
- synthesize lipids that become part of cell membranes
- convert drugs, poisons, and toxins in the liver into tolerable or easily removed substances
what is the golgi complex?
- made of a stack of sacs called cisternae
- proteins made in the ER enter on the cis face delivered by transport molecules that fuse with the membrane
- proteins are chemically modified by removing segments or adding functional groups or lipids and carbs
- modified proteins exit from the trans face
how did eukaryotes evolve from prokaryotes?
- endosymbiosis— when a prokaryotic engulfed a small cell that would evolve into the mitochondria
- the prokaryotic ancestor likely entered the host cell as undigested prey or an internal parasite
why would a host that was an anaerobe benefit from endosymbionts?
it could use the oxygen and over time become a single organism
where did the mitochondria and plastids descend from?
bacterial cells, the original host thought to have been an archaean
where did the mitochondria descend from ?
aerobic heterotrophic bacteria
where did chloroplasts descend from?
cyanobacteria
what are the parts of the endomembrane system and what does it do?
- the nuclear envelope, the ER, and the golgi complex
- characterized eukaryotic cells
- collection of internal membranes dividing the cell into structural and functional regions
what were the ancestors of plastids?
photosynthetic bacteria
what is the morphology evidence in the mitochondria and chloroplasts?
similar features to prokaryotic cells, inner membranes have enzymes and transport systems that are homologous to those found in the plasma membrane of living bacteria
what is the evidence of reproduction in the mitochondria and chloroplasts?
divided by binary fission the same way as prokaryotic cells, mitochondria and plastids replicate by a splitting process that is similar to that of a certain bacteria
what is the evidence of genetic info in the mitochondria and chloroplasts?
contain their own DNA with protein coding and non-coding genes essential for organelle function
how did multicellularity evolve?
differentiation of same species that congregated into colonies producing algae and ancestors of fungi, plants, and animals
what is the cambrian explosion?
many present days animal phyla appear suddenly in fossils early in the cambrian period (sponges, cnidarians, molluscs, snails, clams and relatives
what was a trait of the animals in fossils pre cambrian?
little evidence of predation, appear to have been grazers— feeding on algae, filter feeders or scavengers, not hunters
what were the discovered features of animals during the cambrian explosion?
claws and other features for capturing prey, new defense adaptations such as sharp spines and heavy body armour
what evolutionary venture helped prevent dehydration?
out of aquatic environments associated with adaptations that made it possible to reproduce on land
when do geologists estimate a new continent will form?
roughly 250 million years from now
what is the theory of plate tectonics?
the continents are part of the great plates of earths crust that essentially float on the hot underlying portion of the mantle and movements of the mantle cause the plates to move over time (continental drift)
what occurs at plate boundaries?
- many important geologic processes including the formation of mountains and islands occur at plate boundaries
- can be plates moving away from each other (the north american and eurasian plates)
- can be plates sliding past each other forming regions where earthquakes are common (california)
- can be plates colliding producing new mountains (the himalayans)
what’s a consequence of the continental drift?
promotes allopatric speciation where supercontinent ls break apart, regions that were once connected become isolated
how did the super continent of Pangaea occur and what did it affect?
250 million years ago plate movements brought landmasses together into a supercontinent Pangaea
- ocean basins became deeper which drained shallow coastal seas
- the formation of Pangaea altered the physical environment and climate which drove species to extinction and provided new opportunities for groups of organisms that survived
- organisms were also affected by the climate change
why does a species go extinct?
- its habitat has been destroyed
- it’s environment has changed in a manner unfavourable to the species
ex. ocean temps falling
how does mass extinction occur?
- disruptive changes to the global environment caused the rate of extinction to increase dramatically
- 50% or more of marine species became extinct