biol 214 exam 1: paleobiology and microevolution (lecture 3)

paleobiologists

-discover, describe, and name new fossil species

-analyze the morphology and ecology of extinct organisms

what is the primary source of data about the evolutionary history of many organisms?

fossils

formation of oxygens

organisms buried by sediments or preserved in oxygen-poor environments

why do fossils only form in oxygen-poor environments?

-lack of oxygen greatly slows decomposition

-scavengers and aerobic bacteria quickly break down soft tissues, but cannot survive in anoxic environments

sedimentation

1. rain and runoff constantly erode land

2. eroded soil and rock particles move downstream before settling

3. particles settle to the bottom as sediments, forming successive layers (weight of newer sediments compresses older layers, sand into sandstone and silt or mud into shale)

4. fossils form within layers when the remains of organisms are buried in the accumulating sediments

Fossilization

-fossils usually preserve details of hard structures (bones, teeth, shells, wood, leaves, pollen)

-dissolved minerals replace some parts molecule by molecule, leaving a fossil made of stone

-other fossils form as molds, casts, or impressions in material that is later transformed into solid rock

why do fossil species represent <1% of all the species that have ever lived?

1. soft-bodied organisms do not fossilize as readily as species with hard body parts

2. unlikely to find fossilized remains of species that were rare or locally distributed

3. fossils rarely form in habitats where sediments do not accumulate (e.g. mountain forests)

4. fossils do not last forever (old fossils are much less common than newer ones)

strata

-layers of sedimentary rock that differ in color, mineral composition, particle size, and thickness

-if undisturbed, arranged in order in which they formed (youngest on top)

-can be disturbed by uplifting, warping, or inversion (geological processes)

relative age

-The age of a rock/fossil compared to the ages of rock layers

-fossils found in same stratum have same relative age

how to date fossils' actual ages

-radiometric dating

-dating organic matter

radiometric dating

-the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products

-works best with volcanic rocks

Dating organic matter

dated directly by measuring their content of the radioactive carbon isotope (14C decays to 14N)

fossils as info sources

-only direct source of info we have

-gives info about size and appearance of ancient animals and plants

-allows scientists to analyze how structures were modified as they became adapted for specialized uses

-useful for data on when evolutionary lineages proliferated and when they went extinct

-provides data on geographical distribution of species

-provide indirect data about behavior, physiology, and ecology

biggest form of air pollution today

water vapor

biggest form of air pollution 2.460-2.462 billion years ago during siderian period

O2

great oxidation event

-2.5ish billion years ago

-the change of Earth's atmosphere from reducing to oxidizing, brought about by oxygen-generating photosynthesis

continental drift

-crust broken into irregularly shaped plates of rock that float on semisolid mantle

-currents in mantle cause plates and continents embedded in them to move

-pangaea broke into laurasia and gondwana, which broke into today's continents

why does continental drift matter?

-widespread distribution of many terrestrial groups on pangaea during paleozoic

-large-scale patterns of geographical isolation

-more coastlines = more niches or areas that organism could occupy

continental drift effect on climate

-continents drifted -> latitudinal positions shifted -> huge changes in local temp

-more coastlines moderated temps

effects of volcanic eruptions

-spew ash into atmosphere, blocking sunlight

-lower earth's surface temp by several degrees for as long as a year

effects of tectonic events

release molten rock onto surface of earth, sometimes raising global temps

effects of asteroid strikes

throw massive amts of material into atmosphere, blocking sunlight and potentially altering planet's climate

continuous distribution

live in suitable habitats throughout geographical area

disjunct distributions

-live in widely separated locations

-created by dispersal and vicariance

dispersal

movement of organisms away from their place of origin

vicariance

fragmentation of a once-continuous geographical distribution by external factors

biota

all organisms living in a region

flora

plants

fauna

animals

alfred russel wallace

used biotas to define six biogeographical realms

zoogeographical realms

Contiguous regions on Earth that are occupied by animals with a shared evolutionary history.

australian and neotropical realms

-geographically isolated since mesozoic (45 mil years ago)

-many endemic species (marsupials)

endemic

confined to a particular country or area

why are marsupials so dominant and diverse?

geographical isolation allowed them to diversify in the absence of placental mammals, which outcompeted marsupials in other parts of the world

nearctic and palearctic realms

-north america and eurasia connected by land bridges between eastern north america and western europe

-many plant and animal species on these continents are closely related

convergent evolution

-Process by which unrelated organisms independently evolve similarities when adapting to similar environments

-large portions of entire faunas can develop convergent morphologies

monotremes

-mammals that lay eggs

-represent an early branch of mammalian evolution, retaining ancient traits like egg-laying and a cloaca (a single opening for excretion and reproduction) that were inherited from their reptile-like ancestors

biodiversity

the variety of life in the world or in a particular habitat or ecosystem.

adaptive radiation

-An evolutionary pattern in which many species evolve from a single ancestral species

-rapid speciation produces a cluster of closely related species that occupy different habitats or consume different foods

-often occurs after an ancestral species moves into an unfilled adaptive zone (triggered by demise of successful groups or morphological innovation)

background extinction

extinction caused by slow and steady process of natural selection

drawback to becoming very specific and specialized

lack the flexibility of generalist species when their specific food source, habitat, or climate conditions are disrupted

mass extinction

large numbers of species and lineages that die out over relatively short periods of geological time

permian extinction

-most severe mass extinction event

-end of paleozoic period

-killed all trilobites, many insects and amphibians, and trees of coal swamp forests

cretaceous (k-t) extinction

-last mass extinction (besides the one we are maybe in now)

-half the species on earth, including most dinosaurs, became extinct

Cause of Ordovician extinction

gondwana moved toward south pole, triggering glaciation that cooled the world's climate and lowered sea levels

cause of permian extinction

chain of events that resulted in severe climate warning, triggered by greenhouse gases released by a series of ongoing eruptions

cause of cretaceous extinction

asteroid impact that may have raised a dust cloud that blocked sunlight necessary for photosynthesis

mass extinctions and biodiversity

-temporarily reduce biodiversities

-create evolutionary opportunities

-some species survive because they have highly adaptive traits, large population sizes, or widespread distributions

what do surviving species do after mass extinctions?

-undergo adaptive radiation

-fill adaptive zones that mass extinctions made available

-increase biodiversity

species selection

species with different characteristics increase or decrease in different number at different rates because of a difference in their characteristics

transitional fossils

-Fossils that provide patterns of evolutionary change from the early ancestors to modern life forms.

-rare because transitional forms live only for short periods of geological time in small, localized populations (conditions that discourage broad representation in fossil record)

phyletic gradualism hypothesis

The hypothesis that most morphological change occurs gradually over long periods of time.

punctuated equilibrium hypothesis

idea that evolution occurs in sudden spurts, followed by long periods without noticeable change

evolutionary stasis

No change in allele frequencies is occurring.

illusion of stasis

-other explanation for evolutionary stasis

-phenomenon where a species or a trait appears to remain unchanged over long periods, while rapid, adaptive evolutionary changes are happening at a genetic level

allometric growth

proportioning that helps give a body its specific form

heterochrony

-Evolutionary change in the timing or rate of an organism's development.

-cause morphology of closely related species to differ

Paedomorphosis

the rate of reproductive development accelerates compared with somatic development

exaptation

the process in which existing structures take on new functions through descent with modification

genetic tool kit

-set of tools that each organisms uses in different ways to develop different but related structures/functions

-govern basic design of body plan

-inherited from common ancestor