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Natural Selection and Species Interactions
“Nature has given women so much power….”- Samuel Johnson
The Great Leap Forward
• Starting in 1958, Mao Zedong, leader of the Communist Party of China, initiated a series of policies to transform the country into a modern, industrialized, communist society.
• One of the first actions taken was known as the Four Pests Campaign. This campaign sought to eliminate rats,
flies, mosquitoes, and sparrows.
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The Four Pests Campaign
• Masses of people were mobilized to eradicate the Eurasian Tree Sparrow.
• Tactics included: Banging pots and pans,
preventing the birds from landing, until they were exhausted.
Tearing down nests. Shooting them from the sky
using guns and sling shots.
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“Everyone come and fight sparrows.”
Unintended Consequences
• The sparrows were hunted because they ate grain seeds; reducing crop yields.
• By April of 1960, Chinese leaders came to realize that the sparrows also ate a large number of pest insects, including locusts.
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Unintended Consequences
• The government made a series of other poor agricultural decisions at this time, including: Ordering farmers to increase the density of
their planting by 6 times, believing that the same species of plant would compete with itself.
Deeper plowing of the soil, which brought up sand and rocks instead of more topsoil.
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The Great Famine
• The locust plague, overplanting, and overplowing combined with a severe drought.
• The number of victims is unknown, but estimated between 20-43 million.
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Ecosystems: Everything is Connected
• Components of an ecosystem: Biotic Factors – Living and
once living parts of an ecosystem.
- Ex: Plants, animals, dead matter, waste
Abiotic Factors – Nonliving parts of an ecosystem.
- Ex: Water, rocks, light 7
• An ecosystem is all of the organisms living in an area.
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Organization of Life and the Environment
• Organism – An individual living thing.• Species – A group of organisms able to
breed and fertile offspring.• Population - All members of a species that
live in the same area at the same time.• Biological Community - All populations living
and interacting in an area.• Ecosystem - A biological community and its
physical environment.• Biosphere – All ecosystems in the entire
Earth.
Ecosystem Organization
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What lives where, and why?
• Habitat – Where an organism lives Every organism a range of factors it can
survive in. Ex: Temperature, precipitation, etc.
• Critical Factor - Single factor that is the most critical in determining how species are distributed – who lives in what habitat.
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Tolerance Limits
Tolerance Limits - Minimum and maximum levels beyond which a particular species cannot survive or reproduce.
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Adaptation
• Adaptation – A trait that allows a species to survive more easily and reproduce.
• Evolution - Inheritance of specific genetic traits that control adaptations, giving a species an advantage in an environment.
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Natural Selection
• Natural Selection - Describes process where better competitors survive and reproduce more successfully.
• Caused by: Random mutations – Changes in DNA are
usually bad, but can be beneficial. Selective pressure – Limited resources
mean only the best competitors survive. Sexual selection – Females choose a mate
based on certain characteristics.
Natural Selection
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Artificial Selection
• The selective breeding of organisms by humans for specific characteristics.
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Fig. 4-3, p. 66
Modern humans(Homo sapiens)appear about2 secondsbefore midnight
Recorded humanhistory begins1/4 secondbefore midnight
Origin of life(3.6–3.8 billionyears ago)
Origin of Life
Evidence of Evolution
• Physical Similarities Most animals have
similar bones in their limbs (fins, arms, wings)
• Comparing DNA• Vestigial Structures
Still exist in the body but are no longer needed
Ex: Appendix, wisdom teeth
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Factors Exerting Selective Pressure
• Physiological stress due to inappropriate levels of a critical environmental factor. Moisture, Light, pH
• Predation Organism is hunted and killed by another Includes parasites, bacteria, viruses
• Competition Other organisms attempting to use same
resources• Luck
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Speciation• Given enough time, enough mutations occur
that a new species develops from an old one. When are two groups considered a
different species?- They cannot or will not interbreed to
produce healthy, fertile offspring.
Natural Selection
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Speciation
• Divergent - Separation of one species into new species.
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Speciation
• Convergent - Unrelated organisms evolve to look and act alike. • Not related• Caused by living in
similar environments
Coevolution
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The process of two species evolving in response to long-term interactions witheach other.
Same or Different Species?
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• Crayfish a.k.a. Crawdad a.k.a. Spiny lobster a.k.a. Yabby a.k.a. Crawfish a.k.a. Creekcrab a.k.a. Mudbug
• We need an internationally accepted name!
The Taxonomic Naming System
Scientific Naming System
• Based on the classification system.• Includes the organism’s genus and species
name. Genus is capitalized Species is lower case The scientific name is written in italics
• Scientific name of the crayfish:
Procambarus clarkii
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The Taxonomic Naming System
• Divides organisms into different levels of organization.
Kingdom Phylum Class Order Family Genus Species
• The more levels two organisms have in common, the more related.
How related are they?
Canis lupus lupus
European Wolf
Canis familiaris
Domesticated dog
How related are they?
Archocentrus nigrofasciatus
Convict Cichlid
Corvus splendens
House Crow
Phylogenetic Tree• Also known as a “tree of life”.• Organisms are grouped and classified based
on three characteristics: Physical characteristics DNA Behavioral characteristics
- Mating rituals, territorial, aggression, etc.• The more of these characteristics two
organisms have in common, the more closely related they are according to evolution. 32
Phylogenetic Tree of Life
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From left to right:1.Orangutan2.Gorilla3.Human4.Chimpanzee5.Bonobo
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Ecological Niche
• Habitat - Set of environmental conditions in which a particular organism lives.
• Ecological Niche - Description of role played by
a species in a biological community.
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Specific Types of Niches
• Opportunistic Species - Quickly appear when any opening in an ecosystem arises. Many weeds.
• Pioneer Species – Able to quickly colonize new ground where nothing else is growing.
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Types of Niches
• Keystone Species - A species whose impact on its ecosystem is especially large and influential.
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SPECIES INTERACTIONS
• Predator-Prey Any organism that feeds directly on another
living organism is termed a predator.- The organism that is eaten is the prey.
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Competition
• Intraspecific - Competition among members of the same species. Dispersal
- Seeds sent far away from parent Territoriality
- Each individual defends part of ecosystem Resource Partitioning
- Adults and larvae eat different foods Ex: Caterpillars and butterflies
• Interspecific - Competition between members of different species.
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Resource Partitioning
• -
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Symbiosis
• Symbiosis - Intimate living together of members of two or more species. Commensalism - One member benefits
while other is neither benefited nor harmed.
Mutualism - Both members benefit.
Parasitism - One member benefits at the expense of other.
Example of Symbiosis
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• Barnacles create homes by attaching themselves to whales. The whales are unaffected.
Example of Symbiosis
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• Clownfish have a mucus coating that allows them to live in sea anemones. Their presence attracts other fish for the anemone to eat.
Example of Symbiosis
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• As bison walk through grass, insects are disturbed and fly away. They are eaten by cowbirds.
Example of Symbiosis
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• Ostriches and gazelles feed next to each other. Ostriches have excellent eyesight, while gazelles have stronger senses of hearing and smell.
Example of Symbiosis
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• Mistletoe extracts water and nutrients from the spruce tree directly.
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POPULATION DYNAMICS
• Population Growth Studies of population growth are based on
the idea of biotic potential. Biotic Potential - Potential of a population
to grow in the absence of limitations.
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Exponential Growth
• Exponential growth is graphed as a J curve. Carrying Capacity - Number of individuals
that can be indefinitely supported in a given area.
- Overshoot - When a population surpasses the carrying capacity of its environment.
- Dieback – Population experiences a sudden steep drop.
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Population Oscillations
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Growth to a Stable Population
• Logistic Growth - Growth occurs more slowly as the population approaches carrying capacity due to environmental resistance.
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Limiting Factors
• Environmental Resistance Any factor that slows the growth of a
population. Density-Dependent Factors – Most likely to
affect dense populations.- Disease, Stress, Predation
Density-Independent Factors – Affects dense and diffuse populations evenly.
- Changes in climate, natural disasters
Population Growth Strategies
• There are two main types of growth strategies: K-strategists focus on long-term
development and a long life.- Ideal for stable, predictable
environments. R-strategists focus on reproducing as
much and as quickly as possible.- Ideal for risky, unstable environments.
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(r) Strategies
• Short life• Rapid growth• Early maturity• Many small offspring• Little parental care• Little investment in
individual offspring
• Adapted to unstable environment
• Pioneers, colonizers• Niche generalists• Prey• Regulated mainly by
extrinsic factors• Low trophic level
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(K) Strategies
• Long life• Slower growth• Late maturity• Fewer large
offspring• High parental care
and protection• High investment in
individual offspring
• Adapted to stable environment
• Later stages of succession
• Niche specialists• Predators• Regulated mainly by
intrinsic factors• High trophic level
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COMMUNITY PROPERTIES
• Primary Productivity - Rate of biomass production. Used as an indication of the rate of solar energy conversion to chemical energy. Net Primary Productivity - Energy (amount
of biomass) left after respiration.
Type of Strategist?
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Type of Strategist?
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Community Structure
• Randomly Arranged Individuals live wherever resources are
available.• Clumped
Individuals cluster together for protection, assistance, or resource access.
• Regularly Arranged
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Community Structure
