Natural Selection
Only these types of traits can be acted on by natural selection
What is heritable traits?
These two bears share a recent common ancestor
What are brown and polar bears?
What is time?
This environmental pressure in the Arctic selects for insulating traits in polar bears.
What is extreme cold?
This diagram is used to show evolutionary relationships among bear species.
What is a phylogenetic tree?
This process involves the splitting of one lineage into two distinct species.
What is speciation?
What is genetic variation?
The dot on a tree before it branches off represents this.
Interglacial periods created this between ancestor bear populations as some bears were stuck on ice while others were on land.
What is reproductive isolation?
This is how new gene variations (alleles) appear in a population that allow some bears to better survive Arctic conditions.
What are mutations?
This type of evidence is the most reliable when determining evolutionary relationships.
What is genetic (DNA) comparison?
Bears trapped on the ice went through this process over generations, leading to modern day polar bears who have traits adapted to the sea ice.
What is natural selection?
What is competition?
The similar sizes of skull in brown and polar bear is an example of this.
What is a homologous trait?
Speciation is complete when populations can no longer do this successfully.
What is interbreed (reproduce successfully)?