Biology 2485B Lecture Notes - Lecture 4: Background Extinction Rate, Species Richness, Speciation

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Lecture 4 - Biodiversity & Extinction
January 20, 2018
6:08 PM
Biodiversity
Total variety of all organisms in an area, taking into account the diversity of species, their genes,
their populations, their habitats and their communities
"Total variability of life"
Biodiversity exists at multiple levels
Within any species there is going to be variation in the genetic makeup
o Some of the variation may be between populations
Species
A population or group of populations whose members share certain characteristics and can
interbreed successfully in nature to produce fertile offspring
Second part of this ^ is the biological species concept
o What distinguishes one species from another is whether they can reproduce/interbreed
with each other
What is the total number of species on earth?
Impossible to know with certainty, but estimates range from 2 million to 100 million
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Break down of life forms
Important thing; most things are insects
Species diversity tends to be higher where its…
Hotter
Wetter
Lower elevation
Species richness for vertebrates is greatest in tropical regions with abundant rainfall
Highest diversity - red, yellow and orange
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Most vertebrates are found near the equator (hotter and wetter)
Earth's Species Diversity
Over 1.8 million species described
Estimate that may be up to 100 million species
Most are Insects
Most are thought to occur in tropical rainforests
What do we know about how species diversity has changed over time?
Fossils = preserved remains of organisms that lived long ago
o Most fossils are mineralized remains (rock imprints)
The fossil record shows:
o Life has existed on Earth for at least 3.5 billion years
o The number of species existing at any one time has generally increased through time
In general, the number of species on earth has been gradually increasing over time
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Document Summary

Biodiversity: total variety of all organisms in an area, taking into account the diversity of species, their genes, their populations, their habitats and their communities. Biodiversity exists at multiple levels: within any species there is going to be variation in the genetic makeup, some of the variation may be between populations. Species: a population or group of populations whose members share certain characteristics and can interbreed successfully in nature to produce fertile offspring. Second part of this ^ is the biological species concept: what distinguishes one species from another is whether they can reproduce/interbreed with each other. Impossible to know with certainty, but estimates range from 2 million to 100 million. Spe(cid:272)ies di(cid:448)ersity tends to (cid:271)e higher (cid:449)here its : hotter, wetter. Species richness for vertebrates is greatest in tropical regions with abundant rainfall: highest diversity - red, yellow and orange, most vertebrates are found near the equator (hotter and wetter)

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