Extinction- The basics (Unit 1) Flashcards
Common misconception
Species go extinct because they are inferior.
Are rhinos superior to t-rex’s, are dolphins superior to mosasaurs.
What is inferiority?
As far as we know there is not one superman phenotype or genotype. There is not one type that is superior under all conditions and attendant selection pressures.
Attendant Selection Pressures
Environment conditions, food availability, energy sources, predators, disease, humans.
Inferiority replacement
What traits are adaptive and context dependent.
Still very hard to determine
What does natural selection operate on?
Entire phenotypes and genotypes, NOT individual types. But to simplify our approach we will only look at a few traits.
Adaptive
An organism becomes better fit to live in it’s current habitat.
Cope’s Rule
animals in a population experience directional selection over a lot of time, towards a larger size.
Not a law but a tendency in some groups, especially mammals. (horses or pliosuars)
Why don’t all species folllow Copes rule
If larger size is adaptive, then why don’t all species show it.
Under stable environmental conditions being larger is adaptive. Larger size allows you to compeete with predators and competitors. (intraspecific and interspecific) this increases survival and reproductive rates.
But larger organisms need more food than smaller ones, in unstable environmental conditions when primary productivity is reduced, food becomes scarce.
So large size can be adaptive in one environment will become maladaptive in new conditions.
Primary Productivity
Autotroph (plants and phytoplanton) biomass decrease, and then heterotroph (herbivores, then predators) biomass also decreases.
10% Rule
When energy is passed in an trophic level ecosystem only 10% of energy will be passed on. Due to heat conversion and energy for growth, digestion.
15% rule is only 15% makes it as bodymass
Trophic Level
Position on food chain where organisms are grouped based on feeding relationship.
Saber tooth morphology
Evolved independently at least 6 times amongst vertebrate predators. Currently we know no extant terrestrial saber-tooth predators.
We may seem them again if we wait a really long time. Since their roots do exist.
Selective Pressure
Evolutionary force that causes one phenotype to be more favorable in certain conditions
Humans
Genus homo
Are sabertooth maladaptive
Smilodon around 8.13 million years, humans 2.3. and smilidon is shortest lived of saber tooth
Can we even judge if it’s maladaptive? Have we been around long enough
David Raup says maybe all species eventually go extinct. but teeth lasted a long time we can assume they weren’t always maladaptive. Lowering opinion of extinct species is same of lowering opinion of dead people because they are dead.
