AP biology: 24 origin of species Flashcards
Darwin explored the Galápagos Islands
And discovered plants and animals found nowhere else on Earth
The origin of new species
or speciation
Macroevolution
Refers to evolutionary change above the species level
A species is
a population or group of populations
whose members have the potential to interbreed in nature and
produce viable, fertile offspring
unable to produce viable fertile offspring with members of other populations
Reproductive isolation
Prevents organisms from producing offspring
Is a combination of various reproductive barriers
Prezygotic barriers
Prevent mating or fertilization of ova from two different species
Postzygotic barriers
Often prevent the hybrid zygote from developing into a viable, fertile adult
The biological species concept cannot be applied to
Asexual organisms
Fossils
Organisms about which little is known regarding their reproduction
Speciation can take place with or without
geographic separation
Speciation can occur in two ways
Allopatric speciation
Sympatric speciation
In allopatric speciation
Gene flow is interrupted or reduced when a population is divided into two or more geographically isolated subpopulations
Once geographic separation has occurred
One or both populations may undergo evolutionary change during the period of separation
In sympatric speciation
Speciation takes place in geographically overlapping populations
Polyploidy
Is the presence of extra sets of chromosomes in cells due to accidents during cell division
Has caused the evolution of some plant species
An autopolyploid
Is an individual that has more than two chromosome sets, all derived from a single species
An allopolyploid
Is a species with multiple sets of chromosomes derived from different species
Sympatric speciation
Can also result from the appearance of new ecological niches
In cichlid fish
Sympatric speciation has resulted from nonrandom mating due to sexual selection
In allopatric speciation
A new species forms while geographically isolated from its parent population
In sympatric speciation
The emergence of a reproductive barrier isolates a subset of a population without geographic separation from the parent species
Adaptive radiation
Is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities
The Hawaiian archipelago
Is one of the world’s great showcases of adaptive radiation
Niles Eldredge and Stephen Jay Gould
Used fossils to develop theory
describe these periods of apparent stasis punctuated by sudden change
The punctuated equilibrium model
Contrasts with a model of gradual change throughout a species’ existence
Most novel biological structures
Evolve in many stages from previously existing structures
Example: eye development
Some complex structures, such as the eye
Have had similar functions during all stages of their evolution
Genes that program development
Control the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult
Heterochrony
Is an evolutionary change in the rate or timing of developmental events
Can have a significant impact on body shape
Allometric growth
Is the proportioning that helps give a body its specific form
Different allometric patterns
Contribute to the contrasting shapes of human and chimpanzee skulls
Heterochrony
Has also played a part in the evolution of salamander feet
In paedomorphosis
Growth is accelerated
Mature species retains body features that were juvenile structures in an ancestral species
Homeotic Genes
Determines orientation and number/ type of limbs
For example: where a pair of wings and a pair of legs will develop on a bird
how a flower’s parts are arranged
Homeotic genes= Hox gene example
Provide positional information in the development of fins in fish and limbs in tetrapods
The fossil record
Often shows apparent trends in evolution that may arise because of adaptation to a changing environment
