EVOLUTIONCHAPTERS 10, 11, 12

Theory of Natural Selection• Descent w/ modification and adaptation to the

environment is the basis of Natural Selection.• Inherited better traits/adaptations, produce more

offspring that reach reproductive age.• 4 main points:

AdaptationVariationOverproductionDescent with modification

Adaptation

• Homologous structures– Particular structures that are similar among species, but may

not have the same function.• Ex –

– Shows evidence of adapting to the environment

Adaptation con’t• Vestigial structures– Structures in modern organisms that have no

particular function, that once were functional.– Generally smaller in size.• Ex.

Variation

– Artificial selection• Selective breeding of domesticated plants and

animals for the sole purpose of human usefulness.• Can be completed in a short period of time, Natural

selection does this over a longer period of time.

Variation

• Embryonic development– Embryos of related species

have similar developmental stages.• Study of a multicellular

organism from a fertilized egg into adult hood.

Variation con’t

• Molecular development– The sequencing of amino acids can be compared to

show similarities in DNA.– The closer the DNA, more related an organism is.– The more different DNA, less related the organism is.

Overproduction

• Most species are capable of producing more offspring than the environment can support.– When there are too many individuals in a

population, there will be competition.– Competition will allow the more successful to grow faster and produce

more offspring.

• Offspring will carry some of the genes of the parents that made them better adapted = Fitness.

• The struggle for survival between individuals of the same species = Natural Selection

Descent with Modification• Traits passed on that favor the environment.• Evolutionary Biology – evolution due to response in environmental

change– Modern medicine

• Antibiotics - Kill or slow the growth of bacteria• Resistant bacteria

– Evolves by natural selection– Resistance is transferred to next generation due to gene altering.

• Viruses – vaccines– Pesticides – used to kill insects. Repeated uses is less effective over time

due to resistance.

Microevolution • Change in allele frequency in a population over

time.• Generation to generation change• Natural selection can change distribution of a

trait through: directional, stabilizing or disruptive selection.

• Cause of N.S. = change in alleles, mutations of existing traits.

Ch.11 Evolution of Populations

• Population increases chance of individuals will survive.

• Genetic variations several sources

Genetic Variation• Random process of events of Mutation and Sexual

recombination, causing a change in frequency of alleles. – Mutation – change in DNA, can be passed on to offspring

- changes allele frequency in gene pool.– Recombination – new allele combination

- occurs during meiosis-

• You are more similar to your family members, than the rest of the species.

Gene pool• All the alleles in all the individuals make up a

population. Like a reservoir of genes.

GG

gg

GG

GG

ggGg

G = Greeng = Brown

• Allele frequency – commonality of certain alleles in a population.

G = Greeng = Brown

Gg

GG

GG

gg

GG

gg

alleles for skin color traitTotal alleles = Frequency of G = Frequency of g =

Gene flow

• Exchanging of genes between two separate populations.

• Increase genetic variation in the receiving population

Genetic drift• Change in gene (alleles) pool of a population due to

CHANCE.– Bottleneck effect – natural disasters reduce the population

and gene pool size.– Founder effect – smaller the colony, less available gene

pool. Limited variations among the population

• Sexual selection – Females choose mates based on their traits, so if a male has favorable characteristics, the female will choose him and those traits.

Speciation• Speciation – New species evolves from an existing species, causing Adaptive

radiation.• Adaptive radiation – diversification of organisms into many new descendent

species caused by different environments. Ex. - Cambrian Explosion

– 2 forms• Gradual(ism) – over time, little changes among the species• Punctuated (equilibrium)– Long periods of no change, then

short periods of drastic change in a species.

Isolation of Speciation Barriers between Gene Pools

• Geographic - result of separation of populations due geographic barrier.

• Behavioral – different courtship/ mating rituals

• Temporal – different breeding seasons

• Reproductive/Mechanical – Different reproductive parts

Patterns of Evolution• Convergent – process by which unrelated or distantly related organisms evolve

similar body forms, coloration, organs, and adaptations. Ex. - wings

• Divergent – when two or more adaptations have a common evolutionary origin, but have diverged over evolutionary time.– Adaptive radiation

• Coevolution – – 2 or more species evolve in

response to changes in each other.

Extinctions• Elimination of a species from Earth, due to not being able

to adapt to environment.• Sudden period of time of great loss of species = MASS

EXTINCTIONS– Catastrophic event(s)

• Surviving organisms had new opportunities to change and compete for food, mates and spaces = adaptive radiation

• Fossil record shows:– Evidence of plant / animal extinctions – Biological diversity – speciation/ adaptive radiation

Ch. 12 Fossil record• Traces history of life and allows us to study history of particular

organisms in rock layers• Over time, sediments bury organisms in rock layers. Giving time

period when organism once lived and relative age.– Older layers are farther from the surface, while the younger layer is closer

to the surface.

Formation of Fossils• Over time, soft bodied parts of an organism

are dissolved away and replaced with minerals that calcify.

• Types - – Permineralization – when minerals

replace hard structures– Natural cast – bone or natural tissue is

removed, leaving an impression.

• Types con’t– Trace fossils - imprints left in soil,

by objects.– Amber preserved – organisms is

trapped in tree resin, then buried– Preserved remains – entire

organism is encased; buried by sediment, dust, volcanic ash, tar pits, ice

Dating of Fossils• Scientists use 2 methods to determine the age of fossils.– Relative dating

• Used to identify relative ages of organisms, based upon location in rock layers.

– Absolute dating• Determines specific age of organic or inorganic objects using ISOTOPES• Every isotope has a half-life, number of years it takes 50% of the object to

decay.• Radiometric dating – measures radioactive isotopes using half-life.

– Uranium 238 used to date object, half life of 4.5 billion years– Not found in living things

• Carbon dating – carbon 14– Used to identify relative young fossils.– Half life of 5,730 years– Relatively accurate to 45 - 50,000 years

2 major events of Earth’s History

• Formation of Pangea– 250 mya– End of palezoic period

• Continental Drift– 180 mya to present– Movement of landmasses

due to the movement of the mantle.

– Similar plants and animals on different continents

geology.rutgers.edu/.../Pangea_NB.html

Earth’s History

Divided into a series of time;• Eras – 100 millions/billions of years• Periods – tens of million of years• Epochs – few million yearsEarth’s atmosphere formed about 3.6 bya• Cyanobacteria – photosynthesis• Stromatolites – colonies

Geologic Time Scale

• Earth’s 4 main Eras1. Precambrian: 4.6 bya -540 mya Origin of

Earth crustal plates formed, 1st cells, one-celled organisms – bacteria, blue-

green algae, soft bodied organisms

2. Paleozoic Era: 540 – 250 mya Cambrian explosion90% of marine life extinct; 70% land life extinctCambrian explosion- Multicellular organisms, hard body parts, Marine life, first amphibians, giant Ferns 1st seed plants

Geologic Time Scale con’t

3. Mesozoic Era: 250 – 65 mya Age of Reptiles dinosaurs were dominant, birds, cone bearing plants, flowering

plants, Creataceous extinction - dinosaurs1st direct mammal ancestor3 main periods – Triassic, Jurassic, Creataceous

4. Cenozoic Era: 65 mya to present Recent life mammals evolved, grasses evolved,

Hominids evolved - Homo sapians ancestors, modern homo sapiens 200,000 years ago, last recorded ice age

Human evolution

Primate Evolution

• Hominid – humans and close relatives• Primates - mammals

- upright walking- flexible hands and feet / opposable thumb- eyes forward looking / binocular vision- enlarged brain / body size- rotational arms-

1) Before 5 mya: In Africa, our ancestral lineage and the chimpanzee lineage split.

2) Before 4 mya: The hominid Australopithecus anamensis walked around what is now Kenya on its hind legs.

3) >3 mya: Australopithecus afarensis (“Lucy”) lived in Africa.

4) 2.5 mya: Some hominids made tools by chipping stones to form a cutting edge. There were perhaps four or more species of hominid living in Africa.

5) 2 mya: The first members of the Homo clade, with their relatively large brains, lived in Africa.

6) 1.5 mya: Hand axes were used. Also, hominids had spread out of Africa and into much of Asia and Europe. These hominids included the ancestors of Neanderthals (Homo neanderthalensis) in Europe and Homo erectus in Asia.

7) 100,000 years ago: Human brains reached more or less the current range of sizes. Early Homo sapiens lived in Africa. At the same time, Homo neanderthalensis and Homo erectus lived in other parts of the Old World.

8) 50,000 years ago: Human cultures produced cave paintings and body adornment, and constructed elaborate burials. Also, some groups of modern humans extended their range beyond Africa.

9) 25,000 years ago: Other Homo species had gone extinct, leaving only modern humans, Homo sapiens, spread throughout the Old World.

http://evolution.berkeley.edu/evosite/evo101/IIE2cHumanevop2.shtml

Mammal evolution Prosimians –

oldest living primate groupNocturnal 55-50 myaNative to Madagascar, Africa & Asia

Mammal evolution con’t Anthropoids – human like primates

New world – native America’s, prehensile tail – live in trees

Old world – ground primates – ground dwellingHominids – walk upright - bipedal, opposable thumb; any

human lineage, modern & extinct – Homo Sapiens 200,000 years

Lesser apes - gibbonsGreat apes – orangutans, chimpanzees, gorillas

Formation of Fossils

• Over time, soft bodied parts of an organism are dissolved away and replaced with minerals that calcify.– buried by sediment, dust,

volcanic ash– skeletons, shells, seeds,

insects trapped in amber – imprints or footprints of

organisms– organisms frozen in ice

(wooly mammoth), or trapped in tar pits (saber-toothed tiger)