Early Ideas of Life. Early Environment Earth is about 4.6 billion years old Inhospitable environment Volcanoes spewed gases that helped form early atmosphere.

Early Ideas of Life

Early Environment

Earth is about 4.6 billion years old Inhospitable environment Volcanoes spewed gases that helped

form early atmosphereGases included: water vapor, carbon

dioxide and nitrogenVery little oxygen present

Early Environment

About 3.9 million years ago:Earth cooled enough for water vapor

to condenseMillions of years of rainstorms that

included lightningBetween 3.5-3.9 million years, first

organisms appeared

Rocks

Tell a lot about history of Earth and life

99% of all species on Earth are extinct

Fossils

Evidence of previously living organisms

Occur in sedimentary rock (layers) Usually near water Gentle process

Water carries small rock particles to lakes and seas.

Dead organisms are buried by layers of sediment, which forms new rock.

The preserved remains may later be discovered and studied.

Figure 17-2 Formation of a Fossil

Formation of a Fossil

Fossils

Paleontologist – study ancient life using layers of earth and fossils

Make conclusions:ClimateWhat organism ateGeography of landModern relatives

Relative Dating

Can determine

Is performed by

Drawbacks

Absolute Dating

Comparing Relative and Absolute Dating of Fossils

Compare/Contrast Table

Imprecision and limitations of age data

Difficulty of radioassay laboratory methods

Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock

Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen

Age of fossil with respect to another rock or fossil (that is, older or younger)

Age of a fossil in years

Compare/Contrast Table

Geologic Time Scale - Eras

Precambrian – prokaryotes and eukaryotes

Paleozoic – first vertebrates and invertebrates, fish, amphibians, reptiles, evergreens dominant

Mesozoic – dinosaurs, mammals, birds, flowering plants dominant

Cenozoic – placental mammals, humans

Geologic Time Scale with Key Events

Glaciations; mammals increased; humans

Mammals diversified; grasses

Aquatic reptiles diversified; flowering plants; mass extinction

Dinosaurs diversified; birds

Dinosaurs; small mammals; cone-bearing plants

Reptiles diversified; seed plants; mass extinction

Reptiles; winged insects diversified; coal swamps

Fishes diversified; land vertebrates (primitive amphibians)

Land plants; land animals (arthropods)

Aquatic arthropods; mollusks; vertebrates (jawless fishes)

Marine invertebrates diversified; most animal phyla evolvedAnaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life

Cenozoic

Mesozoic

Paleozoic

PrecambrianTime

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

1.8–present

65–1.8

145–65

208–145

245–208

290–245

363–290

410–363

440–410

505–440

544–505

650–544

Key EventsEra Period Time(millions of years ago)

Geologic Time Scale

Early Life Ideas

People thought that bacteria came from air, maggots came from meat, and baby mice came from sacks of grain

Spontaneous generation is the idea that living things can come from nonliving things.

Early Life Ideas

Spontaneous generation Living things come from non-living things Redi (1668) disproved: “meat in a jar”

Vital force in the air Idea that microorganisms arise from air Pasteur (1880s) disproved: broth in a swan-

necked flask Biogenesis: Life comes from life

Modern Life Ideas

2 things had to happen before life appeared:Organic molecules had to formThese molecules had to organize into

proteins, carbohydrates, and nucleic acids

Modern Life Ideas

Oparin (1930s) - primordial soup hypothesisEnergy from the sun, lightning & heat

triggered chemical reactions to change gases into small organic compounds

Miller-Urey Experiment

1953 - Experiments tested Oparin’s hypothesis

They were able to produce amino acids and other organic compounds in the lab

Later experiments showed that amino acids heated w/o oxygen would form proteins

The First Organic Molecules Miller and Urey’s Experiment

Condensationchamber

Mixture of gases simulatingatmosphere of early Earth

Spark simulatinglightning storms

Watervapor

Liquid containing amino acids and other organiccompounds

Cold water cools chamber, causing droplets to form.

Formation of Microspheres

proteinoid microspheres - large organic molecules form tiny bubbles called under certain conditions are not cells have selectively permeable membranes can store and release energy.

Hypotheses suggest that structures similar to microspheres might have acquired more characteristics of living cells.

The Puzzle of Life's Origin

RNA and the Origin of Life

Abiotic “stew” ofinorganic matter

Simple organicmolecules

RNA nucleotides

RNA able to replicate itself, synthesize proteins, andfunction in information storage

DNA functions in information storage and retrieval

RNA helps inprotein synthesis

Proteins build cellstructures and catalyzechemical reactions

Free Oxygen

Oxygen in the atmosphere drove some life forms to extinction

Other life forms evolved new, more efficient metabolic pathways that used oxygen for respiration.

Endosymbiosis

Margulis (1960s) - Endosymbiotic theory

Eukaryotes came from symbiotic relationships between prokaryotes

Large prokaryotes ingest small prokaryotes --> plant and animal cells

Endosymbiotic Theory

Mitochondrion

Aerobicbacteria

Nuclear envelopeevolving

Ancient Prokaryotes

Plants and plantlike protists

Primitive PhotosyntheticEukaryote

Primitive AerobicEukaryote

Ancient AnaerobicProkaryote

Chloroplast

Animals, fungi, and

non-plantlike protists

Photosynthetic bacteria

Origin of Eukaryotic Cells

Ancient Anaerobic Prokaryote

Nuclear envelopeevolving

Aerobicbacteria

Ancient Prokaryotes

Origin of Eukaryotic Cells• Prokaryotes that

use oxygen to generate energy-rich molecules of ATP evolved into mitochondria.

Mitochondrion

Primitive Aerobic Eukaryote

Origin of Eukaryotic Cells

Primitive Photosynthetic Eukaryote

Chloroplast

Photosynthetic bacteria

Prokaryotes that carried out photosynthesis evolved into chloroplasts.

Concept Map

Evolution of LifeEarly Earth was hot; atmosphere contained poisonous gases.

Earth cooled and oceans condensed.

Simple organic molecules may have formed in the oceans..

Small sequences of RNA may have formed and replicated.

First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.

Later prokaryotes were photosynthetic and produced oxygen.

An oxygenated atmosphere capped by the ozone layer protected Earth.

First eukaryotes may have been communities of prokaryotes.

Multicellular eukaryotes evolved.

Sexual reproduction increased genetic variability, hastening evolution.