Principles of Evolutionand

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

autotrophs

herbivores

Carniv.

When one group outgrows the supporting group the result is

autotrophs

herbivores

Carniv.

herbivores

Carniv.

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

Growth of a population increases over time

Pop

ulat

ion

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)Testosterone

DDT

Diethylstilbestrol

Our Future Depends on the Decisions We Make Today