lec 24- species and their origins Flashcards
how many species of giraffe were thought to exist but how many actually exist?
1 but 6 different giraffe species exist
can two species that were thought to be separate actually be related and one species?
yes
what did Darwin think about species?
undefinable because of the variations and graduations among them
can a single definition cover all living and extinct species?
no
what are the 3 main species concepts out of 25 and their definitions?
- Morphological species concept: focus on overall morphological differences (long used but not favored anymore)
- Biological species concept: species are groups of potentially interbreeding populations that are reproductively isolated from other groups (widely accepted for sexually reproducing organisms)
- Phylogenetic species concept: smallest possible group descending from a common ancestor and recognizable by unique derived traits, based on synpomorphies
what is the 4th new species concept?
linear species concept: species are composed of smaller metapopulations that can exchange alleles frequently enough to comprise the same gene pool
what are metapopulations?
spatially separated populations that still interact and exchange genes
can different species be considered different metapopulations that evolve independently?
yes
who came up with the biological species concept?
Ernst Mayr 1942
what are the two types of isolating barriers?
-geographic: landscape that prevents gene flow
-reproductive: biological features that prevent interbreeding
what has geographic isolation done to the Aberts squirrel?
caused another subspecies to form due to isolation that has different characteristics like a dark body and white tail, called the Kaibab squirrel
both were originally thought to be a separate species
are Elk and Eurasian red deer considered the same species?
yes as they can interbreed but 13 subspecies exist that can be a separate species
what type of isolation do Eurasian red deer and Elk experience?
allopatric isolation
are red and yellow shafted flicker birds considered one species or different?
one species as hybrids can interbreed
are the audubon and Myrtle warbler separate species?
yes
what does hybridization lead to?
introgression, mixing of genes and phenotypic traits in hybrids which can lead to new variants if fertile
what are some types of premating barriers?
-different timing for reproduction between species to prevent hybridization
-mismatched sex organs
-behavioural isolation (different chemoattractants)
can ecological isolation prevent cross breeding between two species?
yes
what are prezygotic barriers?
when sexual gametes from one species fail to penetrate and fertilize the gametes of another species
what are postzygotic barriers?
when hybrids cant reproduce (sterile) or are abnormal (inviability)
what are reproductive barriers?
intrinsic biological features of organisms that reduce likelihood of interbreeding and producing viable offspring
what does hybridization usually act as?
-a species barrier, keeps species distinct as hybrids aren’t well adapted to the environment resulting in death
-hybridization can lead to speciation if they become reproductively isolated from both parents
how did the galapagos Finch evolve in three generations?
hybridization between cactus Finch and ground Finch resulting in offspring only breeding among themselves
