Science Exam: Unit 5 – Flashcards

the trace or remains of an organism that lived long ago, most commonly preserved in sediment rock.

any method of determining whether an event or object is older or younger than other even or object.

any method of measuring the age of an even or object in years.

the standard method used to divide the Earth’s long natural history into manageable parts.

describes a species that has died out completely.

the period in the geologic time scale feom the formation of the Earth to the beginning of the Paleozoic Era, from about 4.6 BYA.

the geologic era that followed the Precambrian time and that was from 543 MYA.

the geologic era that was 248 MYA; also called the “Age of the Reptiles”.

the most recent geological era, 65 MYA; called the “Age of the Mammals”.

a type of mammal characterized by opposable thumbs and binocular vision.

a type of primate characterized by bipedalism, relatively long lower limbs, and lack of tail; examples including humans and their ancestors.

the species of hominids that includes modern humans and their close ancestors and that first appeared about 100,000 to 150,000 years ago.

a historical sequence of life indicated by fossils found in layers of the Earth’s crust.

the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals; a theory explaining the mechanism of evolution.

the period between birth of one generation and the birth of the next generation.

scientist who uses fossils to help them reconstruct the history of life before humans.

shows what life was like on Earth before humans and how it has changed. Traces or imprints of living things. The living have been preserved by geological processes.

• Sediment fossil:
• Sediment: dirt, clay soil; organisms get covered with
• Can be pressed together to form sedimentary rock
• Steps:
• 1. Organism dies and is buried
• 2. Decomposes and leave a mold in the rock
• 3. After a LONG time the mold fills with sediment which makes a cast
• Petrified fossil:
• Mineral replaces bone, shell and other hard parts.
• The organism is trapped and is turned into a rock after a long time.
• Trace Fossil:
• Foot prints, tracks, trails made by living things
• Have found fossils of human ancestors
• Cast:
• Molded in the shape of a living thing or its remains
• Forms when minerals or rocks fill in the mold
• Mold Fossil:
• Space in a rock that has the shape of the remains of a living things that once occupied that space.
• Coprolite fossil:
• Petrified poop
• Can reveal what was eaten
• Imprint fossil:
• Impression of parts of an organism left in sediment or soil before it hardens (dies in the soil)
• Fish, feathers, leaves

• Sedimentary rock has many layers
• Oldest is on the bottom and new on top
• Layers tell scientists the Relative Age of the fossil
• Relative Dating: estimating the age of rocks and fossils by looking at layers
• Absolute Dating: years by chemical testing

➢ Calendar used to outline Earth’s history
➢ Time of formation to now
➢ After dated a fossil is placed in chronological order with others fossils according to the GTS

➢ Block of time is an Era
➢ Characterized by type of organisms that dominated the Earth at the time
➢ 4 Eras:
• Precambrian Era: 4.6 BYA
• Paleozoic Era: 542 MYA
• Mesozoic Era: 251 MYA
• Cenozoic Era (Humans): 65.5 MYA to present

➢ Marks time when large numbers of species disappear from the fossil record—big gap in the GTS
➢ Extinct: species does not appear again
➢ Not sure what could have caused each mass extinction ➢ Dinosaur Mass Extinction= MAY HAVE been caused by extreme changes in climates—could have been a meteorite.

➢ Oldest
➢ When life began
➢ Bottom of the Grand Canyon is from the Precambrian Time
➢ Environmental factors:
• Atmosphere mainly gasses: water vapors, CO2 and Nitrogen.
• Volcanic eruptions
• Meteorite impacts
• Violent storms
• Sever radiation—no ozone yet
➢ How did Life begin?
• 1. Radiation from the sun caused chemicals in the ocean and atmosphere to react
• 2. Created complex molicules which made life possible (eventually formed cells)
• 3. First organism didn’t need oxygen—prokaryotes
• 4. After roughly 1 billion years Eukaryotes evolved—found in fossil record
• 5. Maybe evolved into multicellular organisms.

➢ “Ancient life”
➢ rock contains fossils from sponges, coral, snails, etc.
➢ fish and sharks
➢ most organisms lived in the water/ocean
➢ plants, fungi, and air breathing animals slowly colonized and moved to land
➢ by the end of the Era, fern forests, mosses and conifers covered the Earth—no flowering plants
➢ Progress to land:
• Crawling insects
• Then salamanders like
• Then reptile and winged insects
➢ The largest mass extinction—roughly 90% of the marine species were extinct

➢ “age of the reptile”
➢ surviving reptiles from the Paleozoic era MAY have evolved into different species
➢ DINOSAUR
➢ They dominated for about 150 MY
➢ First birds appeared
➢ Mass Extinction:
• 65 MYA
• hypothesis
• large meteorite hit the Earth; fires, dust and smoke blocked out the sun
• plants died without sun—without plants, the herbivores died—without herbivores, carnivores died—decomposers died—no life

➢ “recent life” or “age of mammals”
➢ fossils closest to Earth’s surface
➢ many mammals, birds, insects, flowering plants appeared for the first time
➢ mammals: mastodon, saber-toothed cats, hominids, Neanderthals, homo sapiens, etc.
➢ climate has changed a lot over years (ex. Ice age)

➢ Mammals include humans, apes, monkeys, and lemurs
➢ Ancestors of primates:
• MAY have coexisted with dinosaurs (cavemen)
• Mouse like and were nocturnal
• Lived in trees and ate insects

➢ Not around until after the dinosaurs went extinct
➢ Roughly 45 MYA
➢ larger brains than primate ancestors
➢ similar to monkeys, apes and humans

➢ Scientists think chimps are the closest living relative to humans
➢ Does not mean humans evolved from chimps
➢ Does mean we share common ancestors
➢ 30 MYA
➢ ancestors of human, chimps, and other apes began to evolve separately.

➢ Family that includes humans and human like ancestors
➢ Bipedalism (walking on two feet)
➢ One famous and recent= Neanderthal
➢ Neanderthal:
• Lived in Europe and Western Asia, roughly 230,000 YA
• Hunted large animals
• Made first fire
• Wore clothing
• Buried their dead with cultural rituals
• Disappeared around 30,000 years ago
• No one knows why: there was no mass extinction

➢ Classified as Homo Sapiens
➢ Earliest in Africa 100,000-160,000 YA
➢ Have smaller, flatter faces and skulls that are round
➢ Only hominids that still exist
➢ Large amount of art—sculptures, carvings, paintings, etc.
➢ Had an organized and complex society
➢ WHO WAS LUCY?
• First skeleton of hominid—40% of bones found in several hundred fragments
• Ethiopia, Asia
• 3ft and 7in tall 65lbs
• named after Beatles hit “Lucy in the sky with diamonds”
• full grown human—had worn wisdom teeth
• wasn’t the oldest, but was the first found
• Australopithecus afarensis