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Islands Introduction
Islands are unique because they are similar
Quick Question #1
What do you think this
statement means?
Refer back to what you
know from rat island
I. Islands Unit Overview
The Story:
•
This unit is about both biological and geological
evolution.
•
Islands provide interesting, unusual examples of
evolutionary change on a scale that is small and
easy to understand.
•
While the results of island evolution tend to be very
different from evolution on a continental landmass,
the mechanisms are the same. Islands simply
become the context to learn evolutionary
mechanisms.
Quick Question #2
Give your best
definition of an island
II. What is an Island?
A. Definition: Islands are isolated environments with unique living
organisms (biology) and unique physical characteristics (geology)
III. Why Do We Study Islands?
A. Islands are unique because they are similar
B. Islands are dynamic and often experience change, both biologically
and geologically, more rapidly than continental landmasses
C. Islands are smaller than continents, therefore easier to study.
D. Islands allow us to study two major themes in science: Evolution
(Biological Science) and Plate Tectonics (Earth Science).
IV. What Happens to Organisms on Islands Over Time?
A. Migrate, Survive, Reproduce, Adapt, Evolve or Go Extinct
Quick Question #3
Predict at least two ways
an Island can form
V. How Do Islands Form?
a. Rising Sea Level
b. Emerging Coral Reefs (Hot Spots)
c. Volcanism
V. How Do Islands Form?
a. Rising Sea Level
• As the sea level rises due to changes in
climate…land masses that were once connected
are now isolated from one another
V. How Do Islands Form?
b. Emerging Coral Reefs
• Coral Polyps and other
marine animals build a
house of limestone
around themselves for
protection
• If the sea level drops or
if the land underneath
rises (hot spots), then
“coral reefs” become
exposed on the surface
• Sand and dust
accumulate on the reef
to form an island
V. How Do Islands Form?
c. Volcanism
• Underwater volcanoes erupt
• As hot lava is emitted from the volcano, it
cools and hardens to form large land
masses on the water’s surface (islands)
Quick Question #4
Compare and Contrast
the three ways islands
can be formed.
VI. What Does Origin of the Island Affect?
•Soil type and composition
•Mineral resources
•Available groundwater
•Ultimately…all life on and around the island
You do not need to take notes on
the next 4 slides/subjects:
VII. Effects on species are unique on islands
VII. Effects on species are unique on islands
A. Species on islands are unique.
Quick Question #5
Predict why all these species grew so large in size on their islands
Elephant Bird - Madagascar
Giant burrowing
cockroach - Australia
Giant Galapagos
Tortoise - Galapagos
Moa
VII. Effects on species are unique on islands
A. Species on islands are unique.
Kiwi Bird - New Zealand
Quick Question #6
Predict why these bird species lost their ability to fly
VII. Effects on species are unique on islands
A. Species on islands are unique.
Quick Question #7
Predict why all these species evolved their traits on their islands
Pygmy hippopotamus – Madagascar
(nocturnal)
Rattleless
rattlesnake - Santa
Catalina Island
Tree climbing kangaroo
- New Guinea
VII. Effects on species are unique on islands
A. Species on islands are unique.
Tasmanian devil - Tasmania
Komodo dragon Komodo Island
VIII. Causes of Uniqueness Are Similar on Islands
The mechanisms that cause islands to be unique:
1. Dispersal Ability – how good a species are at migrating to
new locations
2. Size Change - organisms are larger or smaller than normal
3. Loss of Dispersal Ability - species easily lose ability to
emigrate
4. Endemism - species tend to evolve and remain native to that
area only
VIII. Causes of Uniqueness Are Similar on Islands
(CONT)
The mechanisms that cause islands to be unique:
5. Relictualism - populations are small and have a greater
chance of extinction
6. Loss of Defensive Adaptations - defense capabilities are
reduced in predator-free environments
7. Archipelago Speciation - many species may evolve from
one in the same island group
8. Adaptive Radiation - many species may evolve from one in
the same location because they use different parts of the
habitat
IX. What mode of evolution is repeatedly
shown through the study of Islands?
Speciation!
• First: What Makes a
species?
– A group of individuals
that can interbreed in
nature.
• Definition of Speciation:
The evolutionary
formation of new
biological species,
usually by the division of
a single species into two
or more genetically
distinct ones.
x. Speciation Can occur through
• Geographic
Isolation
• Temporal
(season/time)
Isolation
• Behavioral
isolation
XI. Speciation
Speciation: Bottom Line
• Animals and plants
adapt to their new
environment
• Speciation occurs
when organisms
undergo
Reproductive
Isolation (where
they can no longer
interbreed).
XII. Two main things happen that drive
evolution:
A. Natural Selection - “Best Fit” Survive
•
Ex. Camouflage, size, speed, adaptations, sex
appeal, strength, intelligence, predictable human
impact etc.
B. Genetic Drift - “Lucky” Survive
A. Ex. Extreme weather, isolation, epidemic
diseases, genetic mutations, unequal gender
balance, geologic activity etc.