Transcript Chapter 4 Notes

Evolution and Biodiversity
Chapter 4
Core Case Study: Life on Earth
• Uniquely suited for life
– Temperature range
– Liquid water
– Gravitational mass
– Oxygen
• Organisms contribute to relatively consistent planetary
conditions – resilient and adaptive
• Biodiversity and sustainability
4-1 What Is Biological Evolution
and How Does It Occur?
• Concept 4-1A The scientific theory of evolution
explains how life on earth changes over time
through changes in the genes of populations.
• Concept 4-1B Populations evolve when genes
mutate and give some individuals genetic traits
that enhance their abilities to survive and to
produce offspring with these traits (natural
selection).
Theory of Evolution
• 4.7 billion years
• Explains why life so diverse
• Supported by fossils, chemical analysis
of primitive rock, DNA, and ice cores
Population Changes over Time
• Populations evolve by becoming
genetically different
• Genetic variability – mutation
Natural Selection
• Genetically favorable traits to survive and reproduce
• Trait – heritable and lead to differential reproduction
• Faced with environmental change
– Adapt
– Migrate
– Become extinct
Coevolution
• Changes in gene pool of one species lead
to changes in gene pool of the other
Science Focus: How Did We Become Such
a Powerful Species?
• Key adaptations – also enabled us to
modify environment
• Evolved very recently
• Technology dominates earth’s life support
systems
4-2 How Do Geological and
Climate Changes Affect Evolution?
• Concept 4-2 Tectonic plate movements,
volcanic eruptions, earthquakes, and
climate change have shifted wildlife
habitats, wiped out large numbers of
species, and created opportunities for the
evolution of new species.
Plate Tectonics
• Locations of continents and oceans
determine earth’s climate
• Movement of continents allow species to
move and adapt
• Earthquakes and volcanoes affect
biological evolution
Earth’s Long-term Climate
Changes
• Cooling and warming periods – affect
evolution and extinction of species
• Five mass extinctions
– Eliminated half of the earth’s species
– Many theories why this occurred
• Opportunities for the evolution of new
species
4-3 What Is an Ecological
Niche?
• Concept 4-3 As a result of biological
evolution, each species plays a specific
ecological role called its niche.
Unique Roles for Species
• Generalist species
• Specialist species
• Specialists prone to extinction – giant
panda
Science Focus: Cockroaches
• Existed for 350 million years – 3,500 known species
• Highly adapted, rapidly producing generalists
– Consume almost anything
– Endure food shortage
– Survive everywhere except polar regions
– Avoid predation
• Carry human diseases
4-4 How Do Extinction, Speciation, and
Human Activities Affect Biodiversity?
• Concept 4-4A As environmental conditions
change, the balance between formation of new
species and extinction of existing ones
determines the earth’s biodiversity.
• Concept 4-4B Human activities decrease the
earth’s biodiversity by causing the premature
extinction of species and by destroying or
degrading habitats needed for the development
of new species.
Speciation
• Geographic isolation
• Reproductive isolation
• Millions of years in slow-producing species
• Hundreds of years in rapidly reproducing
species
Extinction
• Endemic species vulnerable to extinction
• Background extinction
• Mass extinction
• Balance between speciation and extinction determines
biodiversity of earth
• Speciation generally more rapid than extinction
Human Activities and Extinction
• Cause premature extinction of species
• Earth took millions of years to recover
from previous mass extinctions
Humans Change Population
Genetics
• Artificial selection – slow process
• Selective breeding
• Crossbreeding – not a form of speciation
• Genetic engineering
Results of Genetic Engineering
• Genetically modified organisms
(GMOs)
• Gene splitting rapid vs. artificial selection
• Modified crops, new drugs, fast-growing
animals
Pros and Cons of Genetic
Engineering
• Pros
– May help cure genetic defects
– May improve organisms
– May lead to development of secondary evolution
• Cons
– Ethical issues
– Privacy issues
– Designer babies
– GMO crossbreeding with original organisms
4-5 How Might Genetic Engineering
Affect the Earth’s Life?
• Concept 4-5 Genetic engineering
enables scientists to transfer genetic traits
between different species – a process that
holds great promise and raises difficult
issues.