Monday, February 20, 2012

Mini Lab: Our Brain's Ability to Ignore Adaptation

 7th grade
Mini labs
IN lab notebooks:

1.       Title
2.       Background notes/ Observations
3.       Problem/question:
4.       Hypothesis
5.       Record data – either in a data table or general observations
6.       Include a Data table when necessary
7.       Include a graph when necessary
8.       Conclusions
9.       Questions to consider


Adaptations: Our brain's ability to ignore unnecessary information

Read the following passage Qucikly. Count the number of (Fs) that you see.


I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg. Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs too.


Termites use trail pheromones to mark a trail which is followed by others. Each individual deposits a small amount of pheromone from a gland onto the surface. The insects also follow certain other chemicals. This effect can be used to show the characteristic trail-following adaptive behavior of the termites.

In biology, `adaptation' refers to the gradual process by which a species becomes
better suited to its environment. For example, humans and monkeys evolved from a
common primate ancestor (Darwin 1859). Psychologists use the term adaptation to refer
to rapid changes in perceptual sensitivity, including the brain's adjustment to brightness
that gives rise to the negative afterimage in the illusion (Clifford and Rhodes 2005).
So, in both senses of the word, our commemorative Darwin Illusion shows adaptation
in action. Basing the illusion around an afterimage also seemed especially appropriate,
given the interests of Charles Darwin's immediate forebears: his father (Robert Darwin)
and grandfather (Erasmus Darwin) both carried out pioneering research into this curious
optical phenomenon (Wade 2002).
image and its negative afterimage each form distinct and meaningful percepts.
The illusion combines two visual effects. First, staring at the picture produces
a negative afterimage, in which the black-and-white pattern is reversed. Second, the
`resolution' of the afterimage is lower than that of the actual image, and so the thin
white lines vanish, making it impossible to see the monkeys (see Harmon and Julesz
1973). To our knowledge, the Darwin Illusion is the first demonstration in which the

Thursday, February 9, 2012

Lines of Evidence for Evolution

1. Homologous Structures!
2. Vestigial Structures!
3. DNA Analysis!
4. Embryological Similarities!
5. Fossil Evidence (Transitional Animals)!

Homologous Structure:

Vestigial Structure

3. DNA - 

- Chimpanzees are 96% to 98% similar to humans, depending on how it is calculated. (source)

- Cats have 90% of homologous genes with humans, 82% with dogs, 80% with cows, 79% with chimpanzees, 69% with rats and 67% with mice. (source)

- Cows (Bos taurus) are 80% genetically similar to humans (source)

- 75% of mouse genes have equivalents in humans (source), 90% of the mouse genome could be lined up with a region on the human genome (source) 99% of mouse genes turn out to have analogues in humans (source)

- The fruit fly (Drosophila) shares about 60% of its DNA with humans (source).

- About 60% of chicken genes correspond to a similar human gene. (source)

The number of genes across a few tested species can be compared on HomoloGene.



5.Fossil Record

Where four limbs evolved in the vertebrate clade

Vertebrate phylogeny with time 

Cladogram of select 
vertebrates showing where certain characters appear

Download this graphic from the Image library.

Friday, February 3, 2012

Geologic Firsts

Three main types of subdivisions of geologic time


Are major subdivisions of the geologic time scale and are based on differences of life forms.

Periods: Based on the type of life existing at the time and on major geologic events like mountain building and plate tectonic movement.
Based on more specific and shorter time periods of life and geologic events.


A group of individuals that breed among themselves to make offspring.

Natural Selection:

The process by which living organisms with traits best suited to an environment survive, while others die out because they lack those desirable traits.

This table is not to any scale.)

Major EventsStart, Million
Years Ago[2]
CenozoicNeogene[3]HoloceneEnd of recent glaciation and rise of modern civilization.0.011430
PleistoceneFlourishing and then extinction of many large mammals (Pleistocene megafauna). Evolution of anatomically modern humans.1.806 *
PlioceneIntensification of present ice age; cool and dry climate. Australopithecines, many of the existing genera of mammals, and recent mollusks appear. Homo habilis appears.5.332 *
MioceneModerate climate; Orogeny in northern hemisphere. Modern mammal and bird families became recognizable. Horses and mastodons diverse. Grasses become ubiquitous. First apes appear.23.03 *
OligoceneWarm climate; Rapid evolution and diversification of fauna, especially mammals. Major evolution and dispersal of modern types of flowering plants33.9 *
EoceneArchaic mammals (e.g. Creodonts, Condylarths, Uintatheres, etc) flourish and continue to develop during the epoch. Appearance of several "modern" mammal families. Primitive whales diversify. First grasses. Reglaciation of Antarctica; current ice age begins.55.8 *
PaleoceneClimate tropical. Modern plants appear; Mammals diversify into a number of primitive lineages following the extinction of the dinosaurs. First large mammals (up to bear or small hippo size).65.5 *
MesozoicCretaceousUpper/LateFlowering plants proliferate, along with new types of insects. More modern teleost fish begin to appear. Ammonites, belemnites, rudist bivalves, echinoids and sponges all common. Many new types of dinosaurs (e.g. Tyrannosaurs, Titanosaurs, duck bills, and horned dinosaurs) evolve on land, as do modern crocodilians; and mosasaurs and modern sharks appear in the sea. Primitive birds gradually replace pterosaurs. Monotremes, marsupials and placental mammals appear. Break up of Gondwana.99.6 *
JurassicUpper/LateGymnosperms (especially conifers, Bennettitales and cycads) and ferns common. Many types of dinosaurs, such as sauropods, carnosaurs, and stegosaurs. Mammals common but small. First birds and lizards. Ichthyosaurs and plesiosaurs diverse. Bivalves, Ammonites and belemnites abundant. Sea urchins very common, along with crinoids, starfish, sponges, and terebratulid and rhynchonellid brachiopods. Breakup of Pangea into Gondwana and Laurasia.161.2
Middle175.6 *
TriassicUpper/LateArchosaurs dominant on land as dinosaurs, in the oceans as Ichthyosaurs and nothosaurs, and in the air as pterosaurs. cynodonts become smaller and more mammal-like, while first mammals and crocodilia appear. Dicrodium flora common on land. Many large aquatic temnospondyl amphibians. Ceratitic ammonoids extremely common. Modern corals and teleost fish appear, as do many modern insect clades.228.0
Lower/Early251.0 *
PaleozoicPermianLopingianLandmasses unite into supercontinent Pangea, creating the Appalachians. End of Permo-Carboniferous glaciation. Synapsid reptiles (pelycosaurs and therapsids) become plentiful, while parareptiles and temnospondyl amphibians remain common. In the mid-Permian, coal-age flora are replaced by cone-bearing gymnosperms (the first true seed plants) and by the first true mosses. Beetles and flies evolve. Marine life flourishes in warm shallow reefs; productid and spiriferid brachiopods, bivalves, forams, and ammonoids all abundant. Permian-Triassic extinction event occurs 251 mya: 95 percent of life on Earth becomes extinct, including all trilobites, graptolites, and blastoids.260.4 *
Guadalupian270.6 *
Cisuralian299.0 *
Upper/LateWinged insects radiate suddenly; some (esp. Protodonata and Palaeodictyoptera) are quite large. Amphibians common and diverse. First reptiles and coal forests (scale trees, ferns, club trees, giant horsetails, Cordaites, etc.). Highest-ever oxygen levels. Goniatites, brachiopods, bryozoa, bivalves, and corals plentiful in the seas. Testate forams proliferate.306.5
Lower/Early318.1 *
Upper/LateLarge primitive trees, first land vertebrates, and amphibious sea-scorpions live amid coal-forming coastal swamps. Lobe-finned rhizodonts are big fresh-water predators. In the oceans, early sharks are common and quite diverse; echinoderms (esp. crinoids and blastoids) abundant. Corals, bryozoa, goniatites and brachiopods (Productida, Spiriferida, etc.) very common. But trilobites and nautiloids decline. Glaciation in East Gondwana.326.4
Lower/Early359.2 *
DevonianUpper/LateFirst clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), first trees (the tree-fern Archaeopteris), and first (wingless) insects. Strophomenid and atrypid brachiopods, rugose and tabulate corals, and crinoids are all abundant in the oceans. Goniatite ammonoids are plentiful, while squid-like coleoids arise. Trilobites and armoured agnaths decline, while jawed fishes (placoderms, lobe-finned and ray-finned fish, and early sharks) rule the seas. First amphibians still aquatic. "Old Red Continent" of Euramerica.385.3 *
Middle397.5 *
Lower/Early416.0 *
SilurianPridoliFirst vascular plants (the whisk ferns and their relatives), first millipedes and arthropleurids on land. First jawed fishes, as well as many armoured jawless fish, populate the seas. Sea-scorpions reach large size. Tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida, etc.), and crinoids all abundant. Trilobites and mollusks diverse; graptolites not as varied.418.7 *
Upper/Late (Ludlow)422.9 *
Wenlock428.2 *
Lower/Early (Llandovery)443.7 *
OrdovicianUpper/LateInvertebrates diversify into many new types (e.g., long straight-shelled cephalopods). Early corals, articulate brachiopods (Orthida, Strophomenida, etc.), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (crinoids, cystoids, starfish, etc.), branched graptolites, and other taxa all common. Conodonts (early planktonic vertebrates) appear. First green plants and fungi on land. Ice age at end of period.460.9 *
Lower/Early488.3 *
CambrianUpper/Late (Furongian)Major diversification of life in the Cambrian Explosion. Many fossils; most modern animal phyla appear. First chordates appear, along with a number of extinct, problematic phyla. Reef-building Archaeocyatha abundant; then vanish. Trilobites, priapulid worms, sponges, inarticulate brachiopods (unhinged lampshells), and many other animals numerous. Anomalocarids are giant predators, while many Ediacaran fauna die out. Prokaryotes, protists (e.g., forams), fungi and algae continue to present day. Gondwana emerges.501.0 *
Lower/Early542.0 *

EdiacaranGood fossils of multi-celled animals. Ediacaran fauna (or Vendobionta) flourish worldwide in seas. Trace fossils of worm-like Trichophycus, etc. First sponges and trilobitomorphs. Enigmatic forms include oval-shaped Dickinsonia, frond-shaped Charniodiscus, and many soft-jellied creatures.630+5/-30 *
CryogenianPossible "snowball Earth" period. Fossils still rare. Rodinia landmass begins to break up.850 [6]
TonianRodinia supercontinent persists. Trace fossils of simple multi-celled eukaryotes. First radiation of dinoflagellate-like acritarchs.1000 [6]
StenianNarrow highly metamorphic belts due to orogeny as supercontinent Rodinia is formed.1200 [6]
EctasianPlatform covers continue to expand. Green algae colonies in the seas.1400 [6]
CalymmianPlatform covers expand.1600 [6]
StatherianFirst complex single-celled life: protists with nuclei. Columbia is the primordial supercontinent.1800 [6]
OrosirianThe atmosphere became oxygenic. Vredefort and Sudbury Basin asteroid impacts. Much orogeny.2050 [6]
RhyacianBushveld Formation occurs. Huronian glaciation.2300 [6]
SiderianOxygen Catastrophe: banded iron formations result.2500 [6]
NeoarcheanStabilization of most modern cratons; possible mantle overturn event.2800 [6]
MesoarcheanFirst stromatolites (probably colonial cyanobacteria). Oldest macrofossils.3200 [6]
PaleoarcheanFirst known oxygen-producing bacteria. Oldest definitive microfossils.3600 [6]
EoarcheanSimple single-celled life (probably bacteria and perhaps archaea). Oldest probable microfossils.3800
Lower Imbrian[8]c.3850
Basin Groups[8]Oldest known rock (4100 mya).c.4150
Cryptic[8]Formation of earth (4570 mya). Oldest known mineral (4400 mya).c.4570

Thursday, February 2, 2012

Earth's five mass extinction events

Earth's five mass extinction events

Earth's five mass extinction events
Posted on 15 April 2010 by John Cook
As climate changes, a major question is whether nature can adapt to the changing conditions? The answer lies in the past. Throughout Earth's history, there have been periods where climate changed dramatically. The response was mass extinction events, when many species went extinct followed by a very slow recovery. The history of coral reefs gives us an insight into the nature of these events as reefs are so enduring and the fossil record of corals is relatively well known (Veron 2008). What we find is reefs were particularly impacted in mass extinctions, taking many millions of years to recover. These intervals are known as "reef gaps".

Mass extinction events and periods of coral reef regrowth

Figure 1: Timeline of mass extinction events. The five named vertical bars indicate mass extinction events. Black rectangles (drawn to scale) represent global reef gaps and brick-pattern shapes show times of prolific reef growth (Veron 2008).

There have been five mass extinction events throughout Earth's history:

The first great mass extinction event took place at the end of the Ordovician, when according to the fossil record, 60% of all genera of both terrestrial and marine life worldwide were exterminated.

360 million years ago in the Late Devonian period, the environment that had clearly nurtured reefs for at least 13 million years turned hostile and the world plunged into the second mass extinction event.
The fossil record of the end Permian mass extinction reveals a staggering loss of life: perhaps 80–95% of all marine species went extinct. Reefs didn't reappear for about 10 million years, the greatest hiatus in reef building in all of Earth history.
The end Triassic mass extinction is estimated to have claimed about half of all marine invertebrates. Around 80% of all land quadrupeds also went extinct.
The end Cretaceous mass extinction 65 million years ago is famously associated with the demise of the dinosaurs. Virtually no large land animals survived. Plants were also greatly affected while tropical marine life was decimated. Global temperature was 6 to 14°C warmer than present with sea levels over 300 metres higher than current levels. At this time, the oceans flooded up to 40% of the continents.
What caused these mass extinctions? To find the major driver of coral extinction, Veron 2008 looks at the possible options and eliminates many as the primary cause. A meteorite strike is capable of creating huge dust clouds that lead to devastating darkness and cold. However, if this were the cause of coral reef extinction, 99% of the world's coral species would be wiped out in weeks or months. The fossil record shows coral extinction occurred over much longer periods.

Warmer temperatures cause mass bleaching of corals. However, even in a warmer world, deep ocean temperatures would still remain well below surface temperatures and there would be safe havens where cooler water upwells from the deep ocean. That's not to say meteorites or global warming played no part in coral extinction - both have been contributing factors at various times. But they cannot fully explain the nature of coral extinctions as observed in the fossil record.

What Veron 2008 found was each mass extinction event corresponded to periods of quickly changing atmospheric CO2. When CO2 changes slowly, the gradual increase allows mixing and buffering of surface layers by deep ocean sinks. Marine organisms also have time to adapt to the new environmental conditions. However, when CO2 increases abruptly, the acidification effects are intensified in shallow waters owing to a lack of mixing. It also gives marine life little time to adapt.

So rate of change is a key variable in nature's ability to adapt. The current rate of change in CO2 levels has no known precedent. Oceans don't respond instantly to a CO2 build-up, so the full effects of acidification take decades to centuries to develop. This means we will have irretrievably committed the Earth to the acidification process long before its effects become anywhere near as obvious as those of mass bleaching today. If we continue business-as-usual CO2 emissions, ocean pH will eventually drop to a point at which a host of other chemical changes such as anoxia (an absence of oxygen) are expected. If this happens, the state of the oceans at the end Cretaceous 65 million years ago will become a reality and the Earth will enter the sixth mass extinction.