Biodiversity and Evolution Flashcards
what is the narrow, more formal definition of evolution
the genetic changes in a population over generations
what is the broad definition of evolution?
change in populations over time
what do genetic changes lead to
modifications in appearance, function or behavior of organisms
what is one of the best supported theories in science
theory of evolution
what is the foundation for modern biology
evolutionary theory
why is evolutionary theory the foundation for modern biology
Knowing how organisms adapt and respond to environments over time is vital for understanding history of life
what does biological evolution result from
RANDOM genetic changes
natural selection
Process where traits that enhance survival and reproduction pass on more frequently to future generations than those that don’t
what can natural selection alter
the genetic makeup of an ENTIRE population
what is the mechanism for evolution
natural selection
what is natural selection based on
unique characteristics seen in the SAME species
does natural selection target a single species or multiple at a time
single species
is natural selection universal for ALL animals
NO - some traits that are beneficial for one species might be disadvantageous for other species
what do species evolve into over time due to natural selection
posses characteristics that lead to better and better success in their given environment
adaptive trait aka adaption
a trait that promotes success
maladaptive trait
a trait that reduces success
what were three observations found by Darwin and Wallace that contributed to natural selection theory
- Organisms produce more offspring than can survive and some are more likely to survive and reproduce than others
- this also insights competition for food, mates, space… - Organisms face a constant struggle to gain enough resources to survive and reproduce
- offspring might inherit the characteristics that give individuals an advantage in surviving and reproducing, and the traits woudl then become more prevalent in the population for future generations
what must a trait be for natural selection
heritable (genes in the DNA code for the trait and its passed along generations)
sources of genetic variation in populations
- mutations (changes in nucleotides in DNA)
- sexual reproduction (recombination)
three ways natural selection can act on genetic variation
- directional selection
- stabilizing selection
- disruptive selection
directional selection
selection that drives a feature/trait in one extreme or the other (not the intermediate)
stabilizing selection
selection that produces the intermediate trait
disruptive selection
selection were traits diverge from their starting condition in BOTH extremes
Stabilizing Selection
Directional Selection
Disruptive selection
Selective pressures
an evolutionary force that causes a particular phenotype to be more favorable in certain environmental conditions.
are all selective pressures the same for each environment
NO
divergent evolution vs convergent evolution
divergent evolution ; two populations of the SAME species, which are geographically separated or reproductively isolated, evolve different traits over time because of adaptation to selective pressures from different environments or habitats.
convergent evolution ; Completely unrelated species develop similar traits because of adaption to selective pressure that are similar in their respective environments
what type of evolution results in speciation
divergent evolution
why does divergent evolution result in speciation
the characteristics of the populations eventually become so different that they are no longer of the same species.
Selective breeding
allowed humans to exaggerate particular traits that we want and “shape” organisms into the desired phenotype (dog breeds)
biodiversity
Total variety of all organisms in an area
what does biodiversity encompass
- species
- genes
- populations
- habitats
- communities
species
a population (or group of populations) of a particular type of organism whose members share certain traits and can interbreed successfully to produce fertile offspring
what is a key aspect of organisms being considered species
the ability to interbreed successfully and produce fertile offspring
Population
A group of individuals of a particular (same) species that live in the same area
Allopatric speciation
Emergence of a new species because of the physical separation of populations over some geographical distance
why does allopatric speciation result in new species
The separation of once one population into more than one results in them unable to breed together and over time the populations will independently form their own genetic variation
what is the test whether speciation has actually occurred
Once the populations become different enough where breeding does not produce viable offspring
when can speciation ONLY occur
if the populations remain isolated for an extended amount of time (if they come back together and breed speciation has NOT occurred)
Sympatric speciation
When two species form from populations that become reproductively isolated, occupying a new ecological role within the SAME geographical area.
examples of sympatric speciation
- the same species mating during different seasons
- species having different mating rituals
- occupying different niches in the same area
What makes each species unique
organisms physical makeup and genetic makeup
Fossils
Preserved remains of organisms (in sedimentary rock) that lived long ago
why are fossils important
tell us about the behaviors, physiology and habitats of dead organisms
how can we figure out how old a fossil is and when the organism lived
by dating the age of the rock where the fossil was found
Fossil record
Cumulative body of fossils world wide, spanning most of geologic time
five things the fossil record shows
- life has existed on earth for 3.5 billion years
- modern organis,s developed from earlier ancestral organisms
- number of species existing at any one time has increased through time
- species alive today are tiny fraction of all species ever lived with the vast majority being extinct
- five major mass extinction events
what determines biodiversity
the appearance (speciation) and disappearance (extinction) of species
Extirpation
disappearance of a species from one part of its normal range
Extinction
Complete disappearance of a species from earth
what can cause extinction
environmental conditions change rapidly or severely enough that a species cannot adapt genetically to the change
are big or small populations MORE vulnerable to extinction
SMALL - fluctuations in their size (by chance) could bring pop to zero
what are some examples of species more susceptible to extinction
- small populations
- species dependent on a specific niche or resource
- endemic species
endemic species
species that occur in only one location on earth, no where else
Background extinction rate
the rate at which extinction of one species occurs
Mass extinctions
Events that killed off massive number of species at once
what do mass extinctions represent
times when biological diversity dropped drastically in short period of time (50%-90%)
what provides the stage for evolution
ecology
levels of hierarchy that ecologists study
ORGANISM level ——> POPULATION level —–> COMMUNITY level ——-> ECOSYSTEM level
organism level
Describes relationships between organisms and physical environment
Population level
Quantitative dynamics of how individuals of the same species interact with one another
Community level
Interactions among species, from one to one interactions to complex interrelationships with entire communities of organisms
Ecosystem level
Focus on patterns of energy and nutrient flow by studying living and nonliving components of systems in conjunction
Habitat
Consists of both living and nonliving elements (rocks, soil, leaves…) as well a other organisms around it
what do motile organisms use in relation to habitats
habitat selection ; actively select habitats from among the range of options they encounter
Niche
A species’ niche reflects its use of resources and its functional role in a community
(habitat use, consumption of foods, role in flow of energy and matter, interactions with other organisms)
Specialists vs Generalists
Specialists ; Species that can survive in only narrow range of habitats that contain very specific resources (Koala or panda)
Generalists ; Species with broad tolerances and can use a wide array of habitats or resources (rats, coyotes…)
Benefits and disadvantages of specialists
Benefit ; Can be successful over evolutionary time by being extremely good at the things they do
disadvantage ; Are vulnerable when condition change and threaten the habitat or resource they have specialized
Benefits and disadvantages of generalists
Benefit ; Succeed by being able to live in a wide variety of places and weather variable conditions
Disadvantage ; May not survive in any one situation to the degree that a specialist would
(Wouldn’t have the specialized skill set that the specialists would have but a more general skill set)
what is important to note about the five mass extinction events
they all have different presumed causes (some my volcanic eruptions, some by climate change, some by asteriods…)
true or false
we may be in a six great extinction because of human affects
TRUE
important ecological concepts
- habitat
- niche
- specialization
