Rates of evolutionary change and extinctions

1. EVOLUTION AND
ADAPTATION
Rate of Evolutionary Change, Endangered Species & Extinction

2. 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

3. 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

4. Gradualism Punctuated equilibrium

5. 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 Endangered
Endangered
Vulnerable

6. 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?

7. 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?

8. What is it?

9. • http://www.onegreenplanet.org/environment/where-have-all-the-pangolins-gone/
• https://youtu.be/gz4HXyxcess

10. 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