EVOLUTION AND ADAPTATION

Rate of Evolutionary Change, Endangered Species & Extinction

Rates of Evolutionary Change: Gradualism

• Evolutionary change that occurs slowly and constantly over time• Based on evidence from fossil record where some organisms have

evolved slowly (in geological time)• Modern organisms have changed very little from ancient organisms

• Ex. Sharks, crocodiles, horseshoe crabs, cockroaches

Rates of Evolutionary Change: Punctuated Equilibrium

• Long periods of stability where little change occurs followed by periods of rapid change to a species

• Caused by environmental conditions such as an ice age. Some species die off, others are able to adapt quickly and survive

• Animals with higher reproductive rates are better able to adapt.• Ex. Mammals, birds

Gradualism Punctuated equilibrium

Endangered Species• Species considered likely to become extinct are categorized by the

International Union for Conservation of Nature (IUCN) • Red List Species are ranked according to their risk of extinction

Percent of total species considered threatened by the IUCN

Critically EndangeredEndangeredVulnerable

Endangered Species & Extinction• Extinction can be natural part of evolution as species fail to adapt

to a changing environment and less fit organisms do not survive.• Human caused/influenced sources of extinction:

• Poaching/Hunting• Habitat destruction• Invasive species• Pollution• Climate change• What else?

Something to think about

• Compare the graph of worldwide threatened species and the numbers of Canadian threatened species

• What group is most at risk worldwide? In Canada?• Why the difference?• Hypothesize why these groups are especially threatened?• Which group is least at risk? Why?

What is it?

• http://www.onegreenplanet.org/environment/where-have-all-the-pangolins-gone/

• https://youtu.be/gz4HXyxcess

Extinction

• Complete disappearance of a species from Earth

• Background extinction – Ongoing extinctions of a few species at a time due to failure to adapt, competition, etc.

• Mass extinction – Extinction caused by catastrophic event that eliminates majority of species. Meteor strike, ice age, climate change etc

• Major geological eras are marked by mass extinctions

• Extinctions leave open niches for other species to adapt to and fill• Extinctions increase speciation