Big Eco Final Test

Speciation

the process by which species are created and destroyed

What are the two ways things go extinct?

cease to exist or go bye bye

organism goes into an evolutionary trajectory and evolve into something else, so their previous form does not exist anymore

Primitive

implies ancestral and old when compared to geologic time (plesiomorphic traits)

Derived

implies recent and advanced (Synapomorphic traits)

Speciation Process

everything that was primitive can evolve and become derived

3 methods of speciation theories

allopatric speciation

sympatric speciation

parapatric speciation

Allopatric Speciation (different land)

a population of a species becomes isolated into 2 sub-populations, organisms then evolve to the specificities of the environment to which they have become isolated

environments are not the same, they are different, animals have to start to respond to the difference

Clinal Variation

variation across the gradient where there are two extremes on the extremes and in the middle there is an average, anything with a large distribution

Allopatric speciation isolation events

Vicariant Speciation

Founder event Speciation

Vicariant Speciation mechanism

climatic or geologic change results in a population becoming split

ex: mountain ranges, rivers, glaciers, watershed shifts, and climate change

Sympatric Speciation (Same Land)

speciation without geographic isolation can occur

occurs on the same land, where generalists create founding stock for future speciation events

speciation follows an evolutionary trend behaviorally towards specialization

Progenitor Form

primarily found in sympatric

Parapatric Speciation

speciation with both geographic and behavioral modalities of speciation

geographically, species are isolated

though they can make contact along a border line, neither species crosses

Adaptive Radiation

adaptations radiate out into new phenotypes and genotypes when an ancestral taxa occupies several new niches or habitats and results in a net gain in species

Microclimate

a very small area that has a different climate

Darwin’s proposal on how long it takes species to form

proposed speciation was a long, gradual process taking thousands to millions of years to occur

Gradualism

the prevailing theory of casual evolution

Gradualism types

Populational Gradualism: new traits become established in a population by increasing their frequency initially from a small fraction of the population to the majority

Phenotypic Gradualism: new traits, even those that are strikingly different from ancestral ones, are produced in a series of small incremental steps

Morphological Divergence

physical representation of gradualism as a graph

What does gradualism NOT explain?

how taxal groups with long evolutionary legacies form or how taxal groups which rapidly form and appear in the fossil record

2 strikes against gradualism

mass extinctions

gaps in the fossil record

Punctuated Equilibrium

relatively recent, theorizes that speciation can occur rapidly, especially ecosystems that have experienced a biological crisis (extinctions)

What happens if several niches are suddenly opened?

speciation rates across taxa increase to occupy those niches

in response to this, speciation occurs rapidly (this can explain gaps in the fossil record and can explain raised levels of diversity immediately following mass extinctions

Natural Selection

“only the strong survive, the weak perish”

strong = ability to reproduce and get to the next generation

From what perspective do biologists view natural selection:

2 faces working towards one goal:

one face points towards an organism’s genotype

from the genotype, the other face is displayed in an organism’s phenotype

Genes that are advantageous

increase an organism’s fitness (which is the goal)

Artificial Selection

to better understand selection in nature, biologists have experimented with selection in controlled settings

How do you complete a cycle of natural selection?

the average fitness of the offspring needs to change

Species phenotypes

species do not have an ideal phenotype, because time does not stop

What occurs when selection is weak or variable in direction?

it cannot act effectively on a population

What is the additional factor that limits natural selection’s impact?

the number of deaths occurring to sexually mature individuals in a population

each individual must ensure that it at least replaces itself to maintain current population levels

What may an organism’s phenotype might be selected for

growth under normal conditions

growth with limited nutrition

growth with limited water intake

disease resistance

What occurs at different times over the course of the species’ existence?

different phenotypes will be successful

What is the species long-term resistance dependent on?

the possibility of the presence of all 4 phenotypes