Campbell Biology 12th edition: Chapter 25

macroevolution

the broad pattern of evolution above the species level (changes over a long time)

products of macroevolution

terrestrial vertebrates, the impact of mass extinctions, origin of key adaptations

conditions of early earth

made the origin of life, chemical and physical processes on early earth may have made simple cells through stages

stages of early earth

abiotic synthesis of small organic molecules, these small molecules form macromolecules, packaging of molecules into protocells, origin of self replicating molecules

when and how earth developed

5 billion years ago

- had no oxygen (Co2, methane...)

- no aerobic organisms

- could make amino acids from inorganic things

- protocells

A.I Oparin and B.S Haldane

thought early atmosphere was a reducing enviornment

Stanley Miller and Harold Urey

developed experiment showing amino acids could form from inorganic materials

"hot vent" studies

- Other studies show that organisms were made around "hot vents" deep in the oceans (gushed hot water and minerals)

- Organisms found there were similar to what used to be in early earth

meteorites

may have been another source of organic molecules

types of hydrothermal vents

black smokers

alkaline vents

black smoker

300 to 400 degrees Celsius

alkaline vents

high pH 9 to 11 (more suitable for the forming of stable organic compounds)

protocells

a vesicle with a membrane structure with beginning molecules packed into it

protocell properties

Replication and metabolism

- key properties of life

- may have appeared together in protocells

- lipids and organic molecules can spontaneously form vesicles with lipid bilayer

first genetic material

probably RNA, not DNA

RNA

- plays important role in protein synthesis

-its ribozymes can catalyze different reactions

(make copies of RNA)

DNA

developed from RNA

(could've made the template for DNA)

fossil records

reveals changes in the history of life on Earth

- sedimentary rock/strata

- hold fossils

- lower down= older

how to become a fossil

- exist for a long time

- have a lot of that species around in population

- have hard parts (shell/skeleton)

how rocks and fossils are dated

The order of fossils in rock strata tells the order in which they were formed

- infer relative age but not actual age

radiometric dating

determining the age of a fossil

- used on fossils 750,000 yr old

what radiometric dating uses

radioactive isotope

- collected while organism was still alive

- ratio of C-14 to C-12

all radioactive materials

have a half-life

"parent" and "daughter" isotope

half-life

time it takes for half of the parent isotope to decay

tetrapod

mammal vertebrae belong to this group of animals

evolution of unique mammalian features

can be traced in the fossil record

ex. mammal jaws evolved gradually over time

geologic record

divided into 4 main eons

4 main eons

Hadean

Archean

Proterozoic

Phanerozoic

Proterozoic era

Neoproterozoic

Phanerozoic

includes the last half billion years

phanerozoic eras

Paleozoic

Mesozoic

Cenozoic

boundaries between eras

correspond to major extinction events in the fossil record

stromatolites

- oldest known fossils

- rocks formed by the accumulation of sedimentary layers on bacterial mats

- 3.5 billion years ago

prokaryotes

the only inhabitant of earth for 1.5 billion years

oxygen revolution

the atmosphere was 1% oxygen then went to 10% very quickly

- caused extinction of many prokaryotic groups

oldest eukaryotic cell fossils

1.8 billion years ago

eukaryotic cell components

nuclear envelope

mitochondria

endoplasmic reticulum

cytoskeleton

eukaryotes origin

- originated by endosymbiosis

- when a prokaryotic cell engulfed a small cell

- evolve into a mitochondrion

endosymbiont

a cell that lives within a host cell

Serial endosymbiosis

mitochondria evolved before plastids through a sequence of endosymbiotic events

mitochondria and plastids

descended from bacterial cells

- original host was likely Archean

evidence supporting endosymbiotic origin

1. inner membranes are similar to bacteria membranes

2. DNA structure and cell division are similar to bacteria

3. both transcribe/translate own DNA

4. ribosomes are similar to bacterial

origin of multicellularity

- evolution of eukaryotic cells allow for a greater range of unicellular forms

second wave of diversification

when multicellularity evolved and gave rise to algae, plants, fungi, and animals

algae

unicellular of multicellular

oldest fossil of multicellular eukaryotes

small red algae from about 1.2 billion years ago

older fossils (multicellular)

1.8 billion years ago

may also be multicellular eukaryotes, but they can't be resolved taxonomically

Ediacaran biota

- assemblage of larger and more diverse soft-bodied organisms

- lived from 635 to 541 million years ago

Cambrian explosion

the sudden appearance of fossils resembling modern animal phyla in the cambrian period (535 million years ago) provide first predator-prey interactions

Fungi, plants, and animals

began to colonize land about 500 million years ago

plants

evolved adaptations to reproduce on land and avoid dehydration

- originally were in the water

ex. a vascular system for transporting materials appeared by about 420 million years ago

plants and fugi

colonized land together

tetrapods evolved from...

lobe-finned fishes around 365 million years ago

human lineage of tetrapods

evolved around 6-7 million years ago

- modern humans originated only 195,000 years ago

rise and fall groups

- history has seen rise and fall of many organism groups

- depend on speciation/extinction rates

sister taxa

Groups that share an immediate common ancestor

Pangea

landmasses of Earth have formed a supercontinent three times over the past billion years

pangea effects

- deepen oceas basins

- reduce shallow-water habitat

- colder and drier inland climate

theory of plate tectonics

earths crust are plates floating on earths mantle leading to changes in climate and living environments

continental drift

movements in the mantle cause the plates to move over time

- tectonic plates are constantly shifting

continental drift effects

- organisms have to respond to climate change (relative to equator)

- separation of landmasses can lead to allopatric speciation

continental drift can

- drift continents apart

- form mountains

- create earthquakes

mass extinction

fossil record shows that most species that have lived in early times are now extinct

extinction

can be caused by changes to a species' biotic or abiotic environment

- rate has increased dramatically

Permian extinction

- defines the boundary between the Paleozoic and Mesozoic eras

- 96% of marine species

252 million years ago

Permian extinction factors

(speculation)

- extreme volcano in current Siberia

- global warming and acidic ocean

- anoxic conditions in ecosystem

Cretaceaous mass Extinction

66 million years ago

More than half of all marine species, terrestrial plants and animals, dinosaurs (except birds) were extinct

- meteorite (nuclear explosion)

Cretaceous meteorite proof

Iridium in sedimentary rock in this time period suggests meteorite impact

Will a sixth mass extinction happen?

yes

- man made extinction

- warning us for a long time

- outpacing what earth can provide

why species decline

habitat loss

intruding species

overharvesting

climate change

adaptive radiation

rapid evolution of diversely adapted species from a common ancestor

adaptive radiation precedents

mass extinctions, evolution of novel characteristics, colonization of new regions

example of adaptive radiation (mammal)

Mammals experienced adaptive radiation after dinosaurs

- more diversity and size

- occur when organisms colonize new areas with small competition

evidence for abiotic synthesis of organic molecules

murchinsons meteorite showing amino acids could form from inorganic materials with energy sources. (volcanoes, hydrothermal vents, electrical charges in deep sea minerals)

evidence for molecules forming macromolecules

2009 study showing polypeptide polymers and simple RNA can form monomers when placed on hot sand/rocks

evidence for packaging molecules into protocells

methods showing the replication and formation of prebiotic lipid vesicles

evidence for self replicating molecules

natural selection requires heritable variation that is only possible from self replicating molecules (an example of ribozymes replicating short nucleotide sequences)