Chapter 6: Evolution and Geography Flashcards
Allopatric speciation
New species arise via the geographic isolation of populations. A physical barrier prevents two or more groups from mating with each other regularly, so the independent lineages follow their own paths and become increasingly different with time.
Ex) warm equatorial water mass
Peripatric speciation. (founder population)
Special version of allopatric speciation.
Occurs when a small, isolated population becomes isolated at the edge of a larger, ancestral population.
The small population is referred to as the founder population
Parapatric speciation
A new species arises within a continuously distributed population.
There is no physical barrier to gene flow, but the population doesn’t not mate randomly. Individuals are more likely to mate with their geographic neighbours than with individuals in a different part of the population’s range.
Sympatric speciation
a new species arises within the range of the ancestral population.
Does not require a physical barrier to reduce gene flow between populations. Instead, exploitation of a different niche, can promote reproductive isolation among populations.
Hybridization
The successful mating between individuals of two different species, resulting in offspring that are not sterile.
Relatively rare in animals. Common in plants.
Population bottlenecks
Reduction in population size and loss of genetic variability.
Causes high rate of hybridization.
Example of biotic factor
Food availability
Example of abiotic factor
Water temperature
Ways to minimise potential heat loss to invironemtn
Large body size, rounded shapes minimising surface to volume ratio, and very good insulation like blubber or fur
Availability of food for marine mammals is established by…
First and foremost by patterns of marine primary production and secondarily by the number of trophic levels between primary production and marine mammal consumer.
Sirenians are the only ones to feed directly on primary producers (sea grasses)
Short summer diatom bloom in polar regions
In polar regions, sea surface temps are always low and the thermocline tends to be weak. The lack of light is the major limiting factor for phytoplankton growth in polar seas.
Sufficient light to sustain high primary production lasts only a few months during the summer. During this time, photosynthesis can continue around the clock and quickly produce huge phytoplankton populations.
El Nino-southerne oscillation (ENSO)
Meteorological and oceanographic phenomenon, which occurs at irregular intervals og 3-10 years. Most obvious characteristic is warming og surface water in the easterne pacific, which blocks the upward transport of deeper, nutrient-rich water from below. –> leads to reduction of zoophytoplankton.
ENSO events heavily affect tropical marine environments
La Nina
Occur when prevailing winds are stronger than usual and result in colder than average temperatures.
Pacific decadal oscillation (PDO)
Long term climate changes.
20-30 year climate patterne results in changes in wind, temp and circulation in the Northern Pacific, affecting marine mammal food resources.
Endemic distribution
Naturally restricted to a particular area
