Descent nt with Modifica catio tion evolutionary change is based - - PDF document

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Chapter er 22 Darwini winian an Evolut utio ion

What t is evolution

• n ?

Descent nt with Modifica catio tion evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness Evoluti tion

• n

change over time in the genetic composition of a population.

Histori storical l Context of Evolu lution ion

Darwin was influenced by many scientists in developing his theory. Aristotl tle 384-322 B.C

• Species are fixed (unchanging)
• Life-forms arranged of scale

(ladder) of increasing complexity (scala naturae)

• Each life form had its permanent

place on the ladder

• Follows Old Testament

(creationism)

• Founder of taxonomy/binomial

nomenclature Domain – Kingdom – Phylum – Class – Order – Family - Genus – Species

• Domains: Eubacteria, Archaea, Eukarya
• Nested system: species grouped into

increasingly general categories

• Classification based on anatomy &

morphology

• Grouped species by resemblances from

pattern of their creation not evolutionary relationships

Carol

• lus Linnaeu

eus 1707-1778 Classified diversity for the “greater glory of God”

Paleontologist – studied fossils

• Deeper strata (layers) - very

different fossils from current life

• Extinctions were common
• ccurrences yet opposed idea of

evolution Catas astr troph phism sm : events destroyed many living species in local areas, then area was repopulated by immigrant species

George e Cuvier ier (1769-1832)

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Geology

• logy

Charles s Lyell 1797-1875

• Gradualism

sm

• Uniform

rmita tari rian anism sm mechanisms of change are slow and constant over time.

• Slow & subtle

changes in

• rganisms lead to

big change James s Hutto ton 1726-1797

• Gradualism

sm: geologic change results from slow, gradual, continuous process still

• perating today.

Jean Lamarck (1744-1829)

1801

• 1. Theor
• ry

y of desire

• organisms change due to inborn desire to change to

become more fit for environment ex: ant eaters develop long snouts

• 2. Theor
• ry

y of use and disuse use

• organs that are being used get large and strong
• organs that are not used shrink and eventually disappear

ex: snakes- didn’t use legs so disappeared

• 3. Theor
• ry

y of inheritance ance

• acquired traits were passed on to offspring

ex: snakes that lost legs passed trait Importan ance ce: Recognized that species evolve, although explanation was flawed

Malthusian sian Doctri rine

• More babies born than

deaths

• Consequences of
• verproducing within

environment: war, famine, disease

• Struggle for existence

Thomas as Malthus (1766-1834) Charl rles s Darwin (1809-1882)

• British naturalist
• Proposed the idea of

evolution by natural ral selecti tion

• Collected clear evidence

to support his ideas

Uniq ique specie ies

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Darwin’s Finches

• Beak variation: an example of adaptive radiation.
• 14 species of finches: evolved from one common

ancestor in South America Darwin’s conclusions

• small populations of original South American

finches reached islands

• variation in beaks enabled some to obtain food

successfully in the different environments

• over many generations, the populations of finches

changed anatomically & behaviorally

• accumulation of advantageous traits
• emergence of different species
• Finches with beak

differences that allowed them to…

• successfully compete
• successfully feed
• successfully reproduce

Other examples of adaptations to food source

1859: : Origin gin of the Specie ies

• Darwin waited 30 years before he

published his ideas on evolution

• Alfred Russell Wallace – published

paper on natural selection first (1858)

• Charles Darwin (1859): On the

Origin of Species by Means of Natural Selection Mechanism for evolution is Natural al Select ction

• n

Darwin didn’t use “evolution”, but rather “desc scent nt with modificat cation

• n”

Origin gin of the Specie ies

Darwin amassed evidence that descent with modification by natural selection explains three broad observations about nature:

• The unity of life: organisms share many characteristics
• The diversity of life: organisms accumulate adaptations
• The match between organisms and their environments

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Darwin’s Theory of Natural Selection

Natura ral selecti tion Individuals that have physical or behavioral traits ts that better suit their r enviro ronment are more likely to survive and will reproduce more success ssfully than those without traits. Parts ts of Theory

• 1. Overp

rpro roducti tion

• organisms produce more offspring than can survive
• leads to competition
• 2. Genetic variat

ation

• individuals in a given species vary by chance

(due to gene recombination) - normal . exception: identical twins

• 3. Struggl

gle to survive

• all organisms face constant struggle to survive

(limited resources)

• 4. Survival

al of the fittest st

• Individuals best adapted to environment are more

likely to survive and reproduce

• Over time favorable traits increase in population

Adaptations enhance an organism’s ability to survive and reproduce. Over long periods of time, steady input

• f new variations in a population

lead to speciation.

DIFFEREN ERENCE CE IN THEORI ORIES ES

Lamarc arck: organisms change in order to survive in environment

• ccurs in the organism’s lifetime

Darwin: environment determines which organisms survive through natural selection

• ccurs

rs over many generat rations

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Evide dences s of Evolution ion

1.

• 1. Direct

t Observ rvat ations

• 2. Fossil record
• 3. Homology

gy homologous & vestigial structures embryology molecular: protein & DNA sequence

• 4. Biogeo

geograpy apy

• 1. Direct Observa

rvation ions

Antibiotic Resistance: MRSA (methicillin-resistant Staphylococcus aureus) Soapberry bug beak length shortened in response to change in food source.

• 2. Fossil record
• Most occur in layers of

rock, with the youngest usually on top, and the

• ldest in deeper layers

(sedimentary rock)

• Some found in amber

(fossilized tree sap)

• Record incomplete due to

soft outer coverings on

• rganisms not leaving

imprints

• 99% of all species that

lived on Earth are now extinct.

Transi siti tional al Species s (links to modern species) Tiktaalik roseae, a 375 million-year-old transitional species between fish and the first legged animals, reveals that the evolution of hind legs actually began as enhanced hind fins.

• 3. Homol
• logy

gy (similari

ariti ties s among organism sms)

Homolo

• logou
• us structures:

: structures which developed from a common ancestor, but have changed over time due to different purposes (diver ergent evolu lution ion)

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Embryologic ryologic similari laritie ies

• evidence of a common

ancestor

• dorsal, hollow nerve cord,

notochord (stiffening rod of cartilage) in the back

• similar membranes in the

embryos, yolk sac that produces the first blood cells and germ cells

• similar development of

many organs

Vestigia gial l organs/ structur tures es:

• Structures which have lost all or most of their
• riginal function in a species through evolution.
• Degenerated, atrophied, or rudimentary condition
• Evidence of change over time

vestiges of pelvic girdle of eyes on nicitating membrane leg bones of walking ancestors blind cave fish

Molecula

lar/ r/ Biochemica ical homologi gies es

• DNA, RNA, amino acids, and serology (comparison of

blood chemistry)

Species Amino Acid Differences from Human Hemoglobin Protein Gorilla 1 Rhesus monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125

Evolu lution

• nary

ry Trees

• Closely related species (branches)

share same line of descent until their divergence from a common ancestor

• Homologous characteristics

that are inherited from a common

• n ancest

stor

• r are strong

indications of evolutionary relationships

• For example, "Tetrapods" all

possess four limbs, presumably because they evolved from an ancest stor

• r (#2) that had four

limbs. Pg 464

Convergen rgent t evolutio ion

• independent evolution of similar features in different lineages
• Distantly reated species resemble one another

Analog logou

• us structures

es: similar in appearance and function, but different origins with different internal structures

• organisms with different ancestors become more alike

because they share same environment

diss ssimilar ar struct ctur ures s  more similar ar struct ctur ures

• 4. Bioge

geogr graphy

• Geographic distribution of a species
• Species in nearby geographic areas resemble each other
• Continenta

tal drift and Pangae gaea explains similarities on different continents

• Endemic species: found at a certain geographic

location and nowhere else ex: Marine iguanas in the Galapagos

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Island d Bioge geograph

• graphy

Natural ral Selection ion vs Artif ific icial ial Selection ion

Natural Selectio ion Artif ificia ial l Selection Nature selects/decides Man selects/decides Acts on individual Selective breeding Population evolves over time Inbreeding occurs Occurs over long periods of time Occurs in short period of time