Download 4.4 Limits on Population Growth

Chapter 4 – Organism and Population
Ecology and Evolution
Photograph by Roger Rothweiler (my brother)
Antarctica 2008
Genetic Change and
Population Growth—Fact and Fiction
• Population growth
– European rabbit in Australia
• Non-native with few predators
• Population exploded
• Genetic change
– DNA controls growth and development
– Environment can alter DNA
• Frogs in Great Lakes
– Pesticides
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4.1 The Cell—The Fundamental Unit of Life
• The cell
– Fundamental unit of life
• Cell structure categorizes
• Prokaryotes
– Small, single celled, DNA in single chromosome
• Eukaryotes
– Single or multicelled
– Membrane-enclosed organelles
– DNA in multiple chromosomes
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.1 The Cell—The Fundamental Unit of Life
• Chemical functions
– Photosynthesis
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Used by plants and some protists and bacteria
Uses sunlight, CO2, and H2O
Produces carbohydrates (sugars) and O2
Carbohydrates power cellular processes
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4.1 The Cell—The Fundamental Unit of Life
• Chemical functions
–Chemosynthesis
• Creates sugars from inorganic chemicals, CO2
and O2
• Used by bacteria in ecosystems with no light
– Ocean depths
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4.1 The Cell—The Fundamental Unit of Life
• Chemical functions
– Cellular respiration
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Carbohydrates broken to power functions
Releases CO2 and H2O
Nearly all organisms use
Requires oxygen (aerobic)
– Anaerobic respiration
• Works without O2
• Yields less energy
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4.2 The Growth and Reproduction of
Organisms
• Asexual reproduction
– Simple cell division
– Genetically identical offspring
• Sexual reproduction
– Requires two individuals
• Gametes produced to form a zygote
– Genetically diverse offspring
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4.3 The Growth of Populations
• Population Growth
– Growth Rate = (Births + Immigration) –
(Death + Emigration)
– Birth rate–births
– Death rate (mortality rate)
– Immigration rate
• Number entering population
– Emigration rate
• Number leaving population
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.3 The Growth of Populations
• Patterns of growth
– Exponential growth
• Growth accelerates with each generation
– Arithmetic growth
• Growth is constant
– Population growth rate
• Percentage of change
– Doubling time
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4.3 The Growth of Populations
• Exponential Growth: A Case Study
• 1890, 60 European starlings released in
NYC
• 10 years later, tens of thousands
• 1920s millions of starlings across New
England
• 1970 starlings across entire United States
• Exponential growth
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4.3 The Growth of Populations
• Survivorship
– Probability of an organism dying during a
particular interval
– Species survivorships vary widely
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Starling vs. bald eagle
Type I–most die old
Type II–young and old die equally
Type III–most die young
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.3 The Growth of Populations
• Fertility rate
– Rate of reproduction
• Changes with age
• Age-specific fertility rates
– Offspring produced at age ranges
• Total fertility rates
– Potential number offspring
– Generation time
• Time between mothers and offspring
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.4 Limits on Population Growth
• Populations cannot grow forever
– Limits to growth
• Carrying capacity
– The number of organisms the environment can support
• Results in logistic growth curve (S shape)
• Competition reduces reproduction rate
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.4 Limits on Population Growth
• Not all populations exhibit an S curve
– Some exceed carrying capacity
• Populations fluctuate around carrying capacity
– Some shoot past carrying capacity
• Population then crashes
– Rather common
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.4 Limits on Population Growth
• Other limits on population growth
– Temperature
– Space
– Chemicals/nutrients
• Range of tolerance
– Span between minimum and maximum values for
survival
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.4 Limits on Population Growth
• Range of tolerance for various factors
determine habitat and niche.
• Habitat
– Environment organism depends on
• Temperature, humidity, living elements
• Niche
– Role organism fills
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4.5 Evolution and Natural Selection
• Species evolve
– Adaptations
• Inherited structure, functions, behaviors
– Give survival, reproductive advantage
– Natural selection
• Most fit leave more offspring, their adaptation
becomes more common
• Less fit have fewer offspring, their adaptation
becomes less common
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4.5 Evolution and Natural Selection
• Biological evolution may occur rapidly
– Recent studies on Darwin's finches
• Droughts caused rapid evolution
• Return of rains reverted population
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4.5 Evolution and Natural Selection
• Source of natural variations
– Mutations
• Chance changes in DNA,
• Environmental influence
– UV radiation, chemicals, pollution
• Random
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4.5 Evolution and Natural Selection
• Three types of natural selection
– Directional selection
• One extreme end of range of variation favored
– Stabilizing selection
• Middle range of variation favored
– Disruptive selection
• Both extremes ends of the variation are favored
over the average traits
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.5 Evolution and Natural Selection
• Other sources of genetic change
–Random events alter frequency of
variations
–Small population susceptible
–Genetic drift
• Founder effect
–Genetics change from immigration of small
group
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4.6 The Evolution of Species
• Species–organisms that can breed and
produce fertile offspring
• New species
– Reproductive isolation
• Breeding barriers
– Geographic
• Mountains, rivers
– Temporal
• Breeding seasons
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4.6 The Evolution of Species
• New species
– Reproductive isolations
• Behavioral
– Courtship rituals
• Structural
– Genital compatibility
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4.7 The Hierarchy of Life
• Taxonomy
– Classification of organisms
• Description, identification, and naming
• Hierarchical system
– Shows evolutionary relationship
– Each level includes level below
– Each species given two-part name
– Genus species,
• Example: Lepus townsendii, Homo sapiens
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
4.7 The Hierarchy of Life
• Organisms classified based on
evolutionary ancestry
– Phylogenetic trees depict ancestry
• Show physical characteristics that classify
• Physical characteristics must reflect evolutionary
ancestry
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