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Chapter 1
Exploring Life: Evolution,
Taxonomy, and Classification
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Background information:
•How long has there been LIFE on Earth? Let’s go back!
–
Formation of the Earth:
•
prob. about 4.6 bya
Evidence of this? Scientific data? Life?
–
Evidence of 1st life forms (microfossils) about 3.5 bya
So, what is the Origin of Life on Earth??? Many ideas...
Some of the hypotheses:
•Intelligent Design, or Special Creation
•Panspermia - Cosmic Origins (from outer space)
•Chemosynthesis (chemical reaction produced organic compounds, possibly cells,
on young planet earth)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
One of the strongest hypotheses is "Chemosynthesis", or
chemical evolution of the first cells on the ancient earth, put forth
by Alexander Oparin (1920's)
• On early earth --->
•volatile atmospheric gases (H2, H2O, CH4, NH3...)
•warm seas
•energy from volcanoes, lightning, UV
• 1st organic compounds formed as a result of this chemical reaction,
much like in a test tube.
• When the seas washed onto shore and the puddles evaporated, the
organic molecules were condensed into "packets" which were able to
sustain themselves; "cells"
•This idea was initially NOT popular in the scientific community; it sounds
an awful lot like spontaneous generation!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Let’s Review: Abiogenesis –vs- Abiogenesis
Abiogenesis: aka “spontaneous generation” of life; used to
be generally believed to be the way that some new life
formed...
...when actually BIOGENESIS was proven using the scientific
method by (among others)
• Francesco REDI- (17th century) "Does life really arise from
rotting meat?“
• Lazzaro SPALLANZANI- (18th c) "Does life arise from
materials in soup broth?" (microbes)
• Louis PASTEUR- (19th c) "Does life arise from materials in
the air?"
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Oparin’s Hypothesis revisited:
...an experiment was tried out in a lab by Stanley
Miller and Harold Urey (1953) who were NOT
able to make cells, but did manage to cook up
some organic molecules necessary for cells
(amino acids, nucleotides, ATP)
Since then, modification of this
experiment have been
explored and some labs have
been able to come up with
some self-sustaining cell-like
things (coacervates,
microspheres)...who
knows? If given a billion years
or so...???
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
So, now that we have 1st cells, what happens next?
Microfossil evidence suggests:
1st forms of life:
 1st prokaryotes: unicellular, simple, anaerobic, heterotrophic
 competition..
---> chemotrophic autotrophs
---> photosynthetic autotrophs
brought about changes on earth...helped to add oxygen to the air...
...atmosphere forming, cloud cover, ozone (protection)
---> first eukaryotes...unicellular, about 1.5 bya; membrane-bound
nucleus and organelles...
“Endosymbiont Hypothesis"
-->first multicellular organisms
about 750 million yrs ago (fossils)
-fairly "recent"!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Evolution is the Unifying Principle of Biology
Evolution accounts for life’s unity and diversity
• The history of life
– Is a saga of a changing Earth billions of years old
Figure 1.17
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The evolutionary view of life
– Came into sharp focus in 1859 when Charles
Darwin published On the Origin of Species by
Natural Selection
Figure 1.18
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Darwin based his
idea on the
understanding of
human-influenced
selective breeding of
domestic animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Darwin’s basic suppositions in “On the Origin of Species…”
• Variation (due to?)
• Competition (for?)
• Natural selection (the environment
decides…)
– “the cruelty of nature”
– “the struggle for existence”
– differential reproduction
– “survival of the fittest” (Herbert
Spencer)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 1.19
Natural Selection
• Darwin proposed natural selection as the
mechanism for evolutionary adaptation of
populations to their environments
Population
of organisms
Hereditary
variations
Define
“adaptation”?
Figure 1.20
Overproduction
and struggle for
existence
Differences in
reproductive success
Evolution of adaptations
in the population
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Natural selection is the evolutionary process that
occurs
– When a population’s heritable variations are exposed
to environmental factors that favor the reproductive
success of some individuals over others
1
Populations with varied inherited traits
2 Elimination of individuals with certain traits.
3 Reproduction of survivors.
Figure 1.21
4 Increasing frequency of traits that enhance
survival and reproductive success.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Each species is on twig of a
branching tree of life
(phylogeny)
– Extending back in time
through ancestral species
more and more remote
• All of life
– Is connected through its
long evolutionary history
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– The products of natural selection are often
exquisite adaptations of organisms to the
special circumstances of their way of life and
their environment
Figure 1.22
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Caution: common features don’t always mean common ancestry!
Convergent evolution:
shaped by the
environment, rather
than shared common
ancestry
Clues: look for
homologous vs
analogous features
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Convergence
http://www.all-about-reptiles.com/convergent-evolution.html
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A Case Study in Natural Selection: Mimicry
• In mimicry
– A harmless species resembles a harmful
species
Flower fly
(non-stinging)
Honeybee (stinging)
Figure 1.26
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Evolutionary Divergence
http://whyevolutionistrue.wordpress.com/2012/07/24/a-new-study-ofpolar-bears-underlines-the-dangers-of-reconstructing-evolution-frommitochondrial-dna/
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Darwin proposed that natural selection
– Could enable an ancestral species to “split” into two or
more descendant species, resulting in a “tree of life”
Large
ground finch
Large cactus
ground finch
Small
ground
finch
Large
tree finch
Camarhynchus
Green
Geospiza
Gray
Geospiza
magnirostris
psitacula
warbler
warbler
Sharp-beaked
fuliginosa
Woodpecker Medium
Geospiza Medium
finch
finch
tree
finch
ground finch
finch
conirostris ground
finch
Certhidea Certhidea
GeospizaCactus
Cactospiza Camarhynchus olivacea fusca
difficilis ground finch
pauper
pallida
Geospiza Mangrove
Small tree finch
finch
fortis
Geospiza
Camarhynchus
Cactospiza
scandens
parvulus
heliobates
Vegetarian
Cactus flower
Seed eater
Seed eater
finch
eater
Platyspiza
crassirostris
Insect eaters
Ground finches
Tree finches
Bud eater
Warbler finches
Ex: Allopatric speciation
Figure 1.23
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Common ancestor from
South American mainland
Unity in the Diversity of Life
• As diverse as life is
– There is also evidence of remarkable unity
15 µm
1.0 µm
Cilia of Paramecium.
The cilia of Paramecium
propel the cell through
pond water.
5 µm
Figure 1.16
Cross section of cilium, as viewed
with an electron microscope
Cilia of windpipe cells. The cells that line the human windpipe
are equipped with cilia that help keep the lungs clean by moving
a film of debris-trapping mucus upward.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Tree of Life
• Many related organisms
– Have very similar
anatomical features,
adapted for their specific
ways of life
• Such examples of kinship
– Connect life’s “unity in
diversity” to Darwin’s
concept of “descent with
modification”
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Drawing evolutionary trees
The phenetic approach is popular with molecular
evolutionists because it relies heavily on character data
- such as sequences - and requires relatively few
assumptions.
In this approach, a tree is constructed by considering
the phenotypic similarities of the species without trying
to understand the evolutionary history that brought the
species to their current phenotypes.
Evolutionary trees (Berkeley)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cladistics bases classification of a
group of species solely on their most
recent common ancestor. Cladistics
uses shared derived characters.
Animation “How to build a cladogram”
YouTube lesson on how to make a cladogram
(10 min)
Practice worksheet
• Concept 1.3: Biologists explore life across its
great diversity of species
• Diversity is a hallmark of life
Figure 1.13
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Classification of Living Things
• Over a million species
named (so far)
• More identified every day
• 2-20 Million left to find?
• Why? Need to organize
information
• Taxonomy = science of
identifying and classifying
organisms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
24
Classifying life
• Taxonomy
– Is the branch
of biology that
names and
classifies
species
according to a
system of
broader and
broader
groups
Species Genus Family
Order
Class
Phylum
Ursus
americanus
(American
black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Figure 1.14
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Eukarya
Kingdom
Domain
The Three Domains of Life
– Distinguished based on
biochemical evidence
(differences in rRNA, genes)
– Domains Archaea and
Bacteria are unicellular
organisms lacking
membrane-bound organelles
like nuclei (Prokaryotes)
– Domain Eukarya is
organisms whose cells have
nuclei (Plants, Animals,
Fungi and Protists)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Classification of Living Things
• 3 Domains
• Kingdom
• Phylum (Division for
plants)
• Class
• Order
• Family
• Genus
•
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Species
27
Domain Archae
• Prokaryotes
– Single celled
– Complex metabolic ability
• Kingdom Archaebacteria
– Found in extreme
environments
– Environments similar to
those of early earth
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– First organisms similar to
Archaea?
28
Domain Bacteria
• Kingdom Eubacteria
–
Found almost everywhere
–
More of them than any other
living thing
–
Some are parasites, causing
diseases
–
Most are harmless and many
are vital to human well being
• Decompose our wastes
• Make vitamins in our guts
• Producing certain products
that we use (yogurt,
cheese)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
29
Domain Eukarya
– Protista- one celled
organisms- producers or
consumers (or both)
– Fungi- molds,
mushrooms; mostly
decomposers
– Plantae- multicellular
plants; mostly producers
– Animalia - multicellular
animals from sponges to
humans; consumers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
30
Classification of Living Things
• Within Kingdoms, organisms are sorted into Phylum,
Class etc.
• At species level organisms so closely related they can
interbreed
• Scientific name = Genus and species names (binomial
nomenclature
ex. Felis catus, Drosophila melanogaster, Homo sapiens
• Genus includes other similar species
ex. F. leo and F. tigris or Quercus rubra, Quercus alba
• Genus ALWAYS starts with cap, species lower case
• Genus and species names are always either underlined or
italicized
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
31
Example: How are humans related to other animals?
Human
House cat
Domain
Eukarya
Eukarya
Kingdom
Animalia
Animalia
Phylum
Chordata
Chordata
Class
Mammalia
Mammalia
Order
Primates
Carnivora
Family
Hominidae
Felidae
Genus
Homo
Felis
Species
sapiens
catus
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
32
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