Ch. 5 Continued Flashcards
Macroevolution
evolution on a large scale (evolution above the species level)
“Why are there more beetle species on the planet than any other insect lineage?” is a macro/microevolution perspective?
Macroevolutionary perspective
“How has natural selection shaped an individual beetle species?” is an example of macro/microevolutionary perspective?
microevolutionary
Specitation
the splitting of one species into two or more
Microevolution and macroevolution are the result of the same processes, it is the _____ that differs.
scale
The same microevolutionary principles that work on a population work to promote/restrict speciation. These include:
- genetic drift
- mutation
- migration
- natural selection
What is the “species problem?”
it is difficult to define the word “species” in a way that applies to all organims
What are the different types of species definitions used?
- Typological species concept
- Ecological species concept
- Phylogenetic species concept
- Biological species concept
- Evolutionary species concept
Typological species concept
a species is a group of organisms conforming to a common morphological plan with fixed properties, emphasizing that species are essentially static
Problems with the typological species concept
- a species may not have many measurable traits (bacteria)
- species are not fixed!
- different phenotypes do not necessarily denote different species
Ecological species concept
a species is a set of organisms adapted to a particular set of resources, called a niche
Niche
the space that an organism occupies
Phylogenetic species concept
a species is the smallest diagnosable cluster of individual organisms, distinct from other clusters, and where there is a parental pattern of ancestry and descent
Biological species concept
groups of actually or potentially interbreeding populations, which are reproductively isolated from other groups
Biological species concept has nothing to do with external appearance, but everything to do with ______ _______.
reproductive isolation
Problems with biological species concept
- What about asexual species?
- fossils?
- hybridization
- reproductive isolation is usually assumed
Evolutionary species concept
a species is a lineage (ancestral-descendant sequence) evolving separately from others and with its own evolutionary roles and tendencies.
Reproductive Isolating Mechanisms
- barriers that prevent successful reproduction
- can be prezygotic
- can be postzygotic
- make it unlikely for hybridization to occur
prezygotic
before mating
postzygotic
occurring after mating
ex. mule exists but can’t reproduce
Prezygotic barriers
prevent reproductive attempts between two individuals
Examples of prezygotic barriers
- habitat isolation
- temporal isolation
- behavioral isolation
- mechanical isolation
- gamete isolation
Habitat isolation
when two species occupy different habitats within the same geographic range; leads to resource partitioning
Resource partitioning
a process where similar species exploit limited resources without overlap
Temporal isolation
reproduction occurs in the same space but at a different time
Behavioral isolation
mate-recognition behaviors that are accepted or ignored between species
Gamete isolation
when sperm and egg are not able to fuse, a zygote cannot form
Mechanical isolation
incompatible genitalia or plant strucutres
Postzygotic barriers
operate after the formation of a zygote and prevent hybrid offspring form developing/reproducing
- hybrid inviability
- hybrid sterility
Hybrid inviability
zygote is not viable and dies
Hybrid sterility
hybrid zygote develops into a sterile adult
Prezygotic isolating mechanisms
- habitat isolation
- temporal isolation
- behavioral isolation
- mechanical isolation
- gamte isolation
Post zygotic isolating mechanisms
- zygote mortality
- hybrid sterility
- F2 fitness
Speciation
the splitting of one species into two or more species
There are multiple modes of speciation but ______ of some sort is a must.
isolation
Isolation can be ______ or _______.
geographic; behavioral
What are the modes of speciation?
- allopatric
- sympatric
Allopatric speciation
speciation when a population becomes separated by a geographic boundary or other physical barrier; once separated, microevolutionary processes can change one population enough so that it becomes reproductively isolated form the other population
Sympatric speciation
speciation in the absence of a geographic barrier
-typically a result of a divergence in diet, microhabitat, or both
Which mode of speciation is less common?
sympatric because there is no physical barrier to observe
In plants, sympatric speciation often involves _______
polyploidy
Polyploid plants can reproduce with themselves but produces _____ offspring when mated to diploid individuals.
sterile
What are the two types of polyploidy?
- autoploidy
- alloploidy
Autoploidy
- occurs when a diploid plant produces diploid gametes during meiosis
- diploid gamete then fuses with haploid gamete
- a triploid plant is the result (sterile)
- ex. banana
Alloploidy
- occurs when two different plant species are able to hybridize
- followed by spontaneous doubling of chromosomes
- produces new hybrid species
Adaptive radiation
-a type of speciation that occurs when a single ancestral species rapidly gives rise to a variety of new species, each of which is adapted to a specific environment
Adaptive radiation is seen in what two scenarios?
- unoccupied ecological space
- the evolution of a novel trait confers a major/new advantage
Ecological release
- landscape-level extinction leaves large areas vacant
- movement into new/unoccupied area
How fast do new species evolve? 2 proposed mechanisms
- gradualism
- punctuated equilibrium
Gradualism
species change gradually from an ancestral species into new species
Punctuated Equilibrium
periods of stasis are punctuated by speciation
