Transcript Principles of evolution

Principles of evolution , our
heritage
and
The Origins of Life
What was life like a long time ago
How did we come into being?
Evolutionary History
• Darwin did not come
up with his theories all
by himself.
• Malthus and others set
up a foundation that
would allow Darwin
to think as he did.
• Others came up with
the same theory
Independently
The “species problem”
• Why do populations of
organisms change over
time?
• If an organism is
present in a particular
area, it must be perfect
for that area, so why
then do exotic species
pose a threat?
Evolution vocabulary words
• Evolution: Change in lines of descent
over time.
• Microevolution: series of changes that
give rise to a new species (population).
• Macroevolution: major large scale
patterns of change in groups of living
organisms.
• Population: a group of individuals of the
same species
• Populations evolve not individuals.
• Populations exhibit great variability.
When this variability changes over time
is when we get new species. (micro
evolution)
• Sources of variation within a population
– mutations create new alleles
– crossing over during meiosis leads to new
combinations of alleles
– independent assortment mixes alleles
Microevolution Processes
•
•
•
•
•
Mutation
Natural selection
Genetic Drift
Gene flow
Reproductive isolation
Mutation
• Any heritable change
in DNA sequence.
• Three types
– lethal mutation
– neutral mutation
– beneficial
• The vast majority of
mutations are probably
invisible or harmful.
Natural selection
• Is the major process to produce populations
that have different characteristics.
• First described by Darwin
– if a trait is more adaptive it improves the
chances of producing offspring (adaptation)
– it gives more of its alleles to the following
generation (greater fitness)
Genetic drift
• Random fluctuation of
allele frequencies over
time
• Works better in small
populations
• Influenced by who
starts a population
– Bottleneck effect
– Founder effect
Gene Flow
• Genes flow with the
individuals of a
population
• Physical flow tends to
minimize genetic
variation, like
shuffling the deck.
Reproductive Isolation and
speciation
• Species: are populations of individuals that
can interbreed.
• When separated by 10,000 or more
generations many species can no longer
interbreed.
• Types of isolation
– geographic, behavioral, biochemical
Rates of evolutionary change
• Gradualism:
Evolution is a slow
and methodical
process
• Punctuated
equilibrium:
Evolution occurs in
rapid bursts followed
by long periods
without change
Evidence for Microevolution
• Biogeography
• Fossil record
• Comparative
morphology
• Comparative
biochemistry
Life Evolved on the Earth about
3.8 Billion Years Ago
• Small organic molecules joined to form
larger molecules
• Genetic material originated
• Organic molecules aggregated into droplets
– Figure 22.4 (p. 514)
A phylogenetic tree
The process of
fossilizaiton
Homologous
structures
Human evolution
We are a class of organisms called
Mammals
Mammals are vertebrates
• Nerve cord
• Vertebrae (backbone)
• Brain
Mammals
• Hair
• Long infancy
(comparatively)
• Flexibility in
responses due to large
brain
• Produce milk
(mammary glands)
Primates
• Monkeys & Apes Physically and
Biochemical similar
Hominoids:
• Chimps and Man
– Common ancestor about 5 million years ago
Evolutionary Trends from
primate to human
•
•
•
•
•
Upright walking
Precision and Power grip
Daytime color vision w/ depth perception
More generalized teeth for omnivore diet
Increase in brain size allows for new and
abstract behavior
Origins of primates
• 60 mya- nighttime omnivores
• 40mya Daytime larger brains
• 35mya ancestor to monkeys and apes and
humans
Humans
• Roughly 200,000 years old (from H. erectus)
• 15,000 years in the Americas
• 35,000 years in Asia decline of Neanderthal
• 2 modes
– Multiregional hypothesis (humans from independent
evolution in europe, asia, africa and Australia
– Out of Africa, one ancestor
We are evolving now
• Our evolution is cultural not morphological
Topic Ecosystems
Biosphere:
the portion of the earth that supports
life: land, air water
Ecology:
• The study of the interactions of organisms
with each other and the environment.
More words:
• Habitat: The place an organism lives
• Community: collections of populations in a
habitat.
• Niche: physical and biological conditions under
which a species can live (an organisms role)
• specialist: has very narrow growth conditions
• generalist: will grow under a wide range of
conditions
Relationships in ecology
Ecosystem
• One or more communities interacting with
one another and with the physical
environment.
Ecosystems will change over
time in a process called:
• Primary succession: life moves onto an area that
previously had no life. Like on a new volcanic
island.
• Secondary succession: When man, fire, floods
disturb a community, a progression of different
forms of life inhabit the area for a while
A human example of succession
The ecosystem organization
Energy from the sun passes through
the ecosystem
The two major classes of life
• Autotrophs: (producers)
– capture sunlight energy and incorporate it into
organic compounds (sugar, Fa, Na, Aa)
• Heterotrophs:
– feed on the tissue products of autotrophs
– Humans and all omnivores and carnivores
The major types of consumers
• Herbivores eat plants
• Carnivores eat animals
• Parasites reside in or on living hosts and extract
energy
• Omnivores eat a variety of organisms
• Detritivores: feed on partially decomposed
organic mater
• Decomposers: reduce waste and dead bodies to
their chemical components
Players in the Ecosystem
A classic food chain
Well things are more like a food
web.
Recycling
• Ecosystems require energy and nutrients
they lose energy and give off nutrients
Recycling of components again
• Unlike physical matter energy cannot be
recycled
– energy that is not passed on to the next tropic
level is lost in the form of heat.
• Trophic levels: A hierarchy of energy
transfers
– each level feeds on the lower level.
Trophic Levels
Energy lost
as heat
Energy lost
as heat
Energy lost
as heat
Pyramids of energy
When one group outgrows the
supporting group the result is
Carniv.
Carniv.
herbivores
herbivores
autotrophs
autotrophs
Biological magnification
Biogeochemical cycles
• The Hydrologic cycle: How water is moved.
• The carbon cycle
– Important in global warming and the greenhouse effect
• The Nitrogen cycle
– An air intermediate moves these atoms across the
planet
• The Phosphorus cycle
– Intense competition of plants and bacteria
Impacts of Human Populations
• Increasing #’s. The worlds population is
still growing.
– Birth control programs have not been
successful
Population dynamics
• Population density- individuals per unit area
• distribution patterns– clumped,
random,
uniform
SF Bay area
Age structure of a population
• Preproductive:
– before sexual maturity
• Reproductive:
– 15-44 age when producing young
• Post reproductive:
– after sexual activity
Population growth
• (births + immunization) - (death + emigration)
• Rate of increase - zero is a balance between
births and deaths
Population
Growth of a population increases
over time
Time
Biotic Potential
• Maximum growth rate of a population given
low death rates
• Depends on
– # of offspring per individual
– time until sexual maturity
– length of sexual maturity
Actual rates of population
increase
• Are influenced by environmental conditions
• Usually biotic potential is not reached
because of rate limiting conditions
• Limits include
–
–
–
–
disease
space
pollution
predation
Carrying capacity
• The number of individuals that a given area
can support
• Mankind has been very effective in
increasing the carrying capacity of the earth.
Human Population growth
• Preindustrial:
– Birthrates & deathrates are high population is level over
time
• Transitional
– birth rates are high death rates are low population
increases
• Postindustrial
– birth rates drop & death rates are low population levels
off
Things that will affect our future
Effects of air pollution
•
•
•
•
Industrial Grey smog
Brown automotive smog
Acid deposition
Damage to ozone
Water scarcity and pollution
• 1/3 of food is from irrigated fields
– irrigation causes salt buildup
– increase in human population causes an
increase in waste, insecticides, chemicals and
pollution
Coping with solid waste
• Loosing places to store waste (recycle)
• Desertification is caused by overusing
marginal lands
We often times put limits on
ourselves
Sex hormones and sex hormone
mimics
Estrogen (Estradiol)
DDT
Testosterone
Diethylstilbestrol
Our Future Depends on the
Decisions We Make Today
Good luck on your final Exam