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BIOL 113 Chapter 17
Terms in this set (42)
How old is the earth?
Scientists estimate that the earth is approximately 4.54 billion years
The earth's age is determined by radiometric dating of igneous rock - a rock formed when molten lava cools and hardens
Scientists use these rocks from moon and earth
Fossils are usually found in sedimentary rock
The use of radioactive isotopes as a measure for determining the age of a rock or fossil. (pg 374)
An unstable form of an element that decays into another element by radiation, that is, by emitting energetic particles. (pg 374)
The time it takes for one-half of a sample of a radioactive isotope to decay. (pg 374)
When and how did life begin? (Biochemistry)
Some scientists hypothesize that life emerged in successive stages over time
Urey and Miller (1953) replicated the chemical environment of the early atmosphere in a flask filled with gases (H2, CH4, NH3, H2O)
- They simulated lightening with electrical sparks producing organic molecules including amino acids
Others followed - came up with same results
Lipid molecules could have formed "bubbles" that incorporated other organic molecules = cell precursors
What was life like a million years ago? (Paleontology)
See flashcards 7-16 (pg 377-379)
Earth's surface cooled (45-85oC) - supported early life about 3.8 bill years ago
Unicellular prokaryotes were the first forms of life with fossils dated at 3.5 billion years
- very little to no oxygen
- used other gases as fuel sources
Stromatolites: Early Prokaryotes
Unicellular photosynthetic organisms added oxygen to the atmosphere; more complex life forms appeared
Ancestors of modern day cyanobacteria might have thrived on the earth 3-2.5 bill. years ago
Origin of Eukaryotic Cells
First Multicellular Life
The first multicellular eukaryotes were green algae (1.2 billion years ago)
- First used oxygen
- Volvox, modern colonial algae, may have resembled the first multicellular eukaryotes
Unicellular choano-flagellates can form colonies
These colonial organisms could have been precursors to multicellular animals
~ 600-550 mya many diverse invertebrate animals (without backbones) appeared in the oceans during the Cambrian Explosion - fossil evidence
This explosion could be due to predator/prey, increase in oxygen, Hox genes (structure and orientation) leading to exploitation of new resources
Led to 20-30 animal phyla that exists today plus extinct gps.
Plants were the 1st organisms to colonize land (450 mya) followed by animals (spiders, millipedes)
First plants nonvascular (mosses, liverworts today), followed by seedless plants and then the rest
The elimination of all individuals in a species; extinction may occur over time or in a sudden mass die off. (pg 379)
The spreading and diversification of organisms that occur when they colonize a new habitat. (pg 379)
An extinction of between 50% and 90% of all species that occurs relatively rapidly. (pf 379)
Permian extinction (250 mya)
95% of all living species went extinct
Survivors spread and diversified
Colonized newly open habitats
Adaptive radiation (Ex: Reptiles)
Cretaceous extinction (65 mya)
Dinosaurs died out
- Following the Cretaceous extinction, mammals underwent an adaptive radiation.
- Pattern of extinctions followed by adaptive radiation is seen in the fossil record
Periodic bursts of species change as a result of sudden environmental change. (pg 379)
Mammals show a punctuated equilibrium after extinction of the dinosaurs
Why are there no penguins at the north pole, and no polar bears at the south pole? (Biogeography)
Distribution of organisms reflects their evolutionary history
250 mya the continents formed one large landmass called Pangaea
Due to plate tectonics, Pangaea split forming today's continents and separating organisms
Islands and isolated land areas have evolved their own flora and fauna. Ex:, penguins inhabit Antarctica (65mya); polar bears, the Arctic (150,000 yrs)
The study of how organisms are distributed in geographical space. (pg 380)
The movement of Earth's upper mantle and crust, which influences the geographical distribution of landmasses and organisms. (pg 381)
Are creatures that look alike always closely related? (Convergent evolution)
Common ancestry is not the only reason that two species might appear similar
The process by which organisms that are not closely related evolve similar adaptations as a result of independent episodes of natural selection. (pg 381)
Cold dwelling fish: Both Arctic and Antarctic fish have "antifreeze" glycoproteins - prevent their body fluids from freezing. These 2 antifreeze proteins coded by diff. genes
Sugar Gliders & Flying Squirrels: The ability to glide through the air evolved independently.
Placental mammals and Marsupial mammals are independent groups that have convergently evolved similar adaptations.
How many species are there on Earth, and how do scientists keep track of them? (Diversity and taxonomy)
Estimated 5 million to 30 million total number of species on Earth
1.5 million or so have been formally described
The process of identifying, naming, and classifying organisms on the basis of shared traits. (pg 382)
Taxonomy is part of systematics, or the study of biological diversity on earth
Taxonomic hierarchy of classification
Domain, kingdom, phylum, class, order, family, genus, species (listed from general to specific)
The categories are increasingly exclusive, until finally only one member is included
Animals with rigid backbones. (pg 383)
Members of the class Mammalia; all members of this class have mammary glands and a body covered with hair. (pg 383)
Is a crocodile more closely related to a bird or a lizard? (Reading phylogenetic trees)
The more recently two groups share a common ancestor, the more closely related they are.
A crocodile is more closely related to a bird.
The evolutionary history of a group of organisms. (pg 384)
A branching diagram of relationships showing common ancestry. (pg 384)
Common ancestor of tree
Common ancestor shared by organisms above this point on tree
Process of natural selection leading to new species or groups of species
How many branches does the tree of life have? (Classification and phylogeny)
Since each living species sits on its own branch in a phylogenetic tree, the complete tree of life has as many branches as there are species in the world
Evidence for Constructing Phylogenetic Trees
Shared DNA Sequence (rRNA genes)
Genus + species = Scientific Name
For example: Lupinus texensis
(Genus - upper case; species - lower case)
History of Classification
- Prior to the 18th century, biologists divided living organisms into 2 main categories:
plants & animals
- In the 19th century the microscope revealed microscopic organisms adding a third category:
- In the 1960's, Whittaker proposed the 5 kingdom system based on structure and function:
Animalia, Plantae, Fungi, Protista, and Monera (prokaryotes)
- In the 1990's, Woese grouped organisms into 3 domains based on rRNA gene sequences:
Bacteria, Archaea, and Eukarya
The highest category in the modern system of classification
There are three domains - Bacteria, Archaea, and Eukarya. (pg 386)
The Three Domains of Classification
Bacteria, Archaea, and Eukarya
Bacteria and Archaea include prokaryotic organisms.
Eukarya includes all the eukaryotic organisms.
- Kingdoms - Animalia, Plantae, and Fungi
- Protista has been subdivided into various Eukarya kingdoms
The age of Earth is determined by measuring the amount of radioactive isotopes present in rocks (radiometric dating).
Life on Earth emerged in stages, as inorganic molecules combined to form organic ones.
Earth's history can be divided into important eras and periods.
History of life on Earth is marked by repeated extinctions and adaptive radiations (punctuated equilibrium).
Ancient movement of Earth's major landmasses affected the eventual distribution of species.
Convergent evolution is the evolution of similar adaptations in response to similar environmental challenges.
Biologists sort organisms into a series of nested categories based on shared anatomical and genetic features.
Driving Question 1: What do we know about the history of life on Earth, and how do we know it?
Driving Question 2: What factors help to explain the distribution of species on Earth?
Driving Question 3: What are the major groups of organisms, and how are organisms placed in groups?
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