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Biology and Society:
Does Biodiversity Matter?
– The expanding human population
threatens
• Biodiversity
• The loss of natural ecosystems
© 2010 Pearson Education, Inc.
THE LOSS OF BIODIVERSITY
– Biological diversity, or biodiversity, includes
• Genetic diversity
• Species diversity
• Ecosystem diversity
Genetic Diversity
– The genetic diversity within
populations of a species is the
raw material that makes
microevolution and adaptation to
the environment possible.
– Genetic resources for that species
are lost if
• Local populations are lost
• The number of individuals in a
species declines
– Cultivated wheat is an example of
a species with limited diversity,
now threatened with the
emergence of a parasitic fungus.
Species Diversity
– Ecologists believe that we are pushing species
toward extinction at an alarming rate.
– The present rate of species loss
• May be 1,000 times higher than at any time in the
past 100,000 years
• May result in the loss of half of all living plant and
animal species by the end of this century
A Chinese river dolphin
Golden toads
These species are now extinct.
Ecosystem Diversity
– The local extinction of one species can have a
negative effect on the entire ecosystem.
– The loss of ecosystems risks the loss of
ecosystem services, including
• Air and water purification
• Climate regulation
• Erosion control
–Coral reefs are rich in
species diversity, yet
•An estimated 20% of the
world’s coral reefs have been
destroyed by human activities
•24% are in imminent danger
of collapse
Causes of Declining Biodiversity
– Ecologists have identified four main factors
responsible for the loss of biodiversity:
•
•
•
•
Habitat destruction and fragmentation
Invasive species
Overexploitation
Pollution
Habitat Destruction
– Biodiversity is threatened by the destruction and
fragmentation of habitats by
•
•
•
•
Agriculture
Urban development
Forestry
Mining
Invasive Species
– Invasive species have
• Competed with native species
• Preyed upon native species
• Parasitized native species
http://www.invasivespeci
esinfo.gov/unitedstates/
wa.shtml#thr
Scotch broom
Overexploitation
– People have overexploited wildlife by harvesting at rates
that exceed the ability of populations to rebound.
– Excessive harvesting has greatly affected populations of
•
•
•
•
•
•
Tigers
Whales
The American bison
Galápagos tortoises
Tuna
Etc…..
Pollution
– Acid precipitation is a threat to
• Forest ecosystems
• Aquatic ecosystems
– Aquatic ecosystems may be polluted by toxic
• Chemicals
• Nutrients
A forest killed by
acid rain
Biodiversity
Important to understand to be able to stop its decline
The Evolution of Biological Novelty
• “What Darwin Never Knew”:
Evidence that LARGE biological changes can be
brought about through small changes during
embryonic development.
• Examples: limbs,
thumbs, big brains
This can help to generate
new species through
evolutionary processes!
1.78 million species
catalogued to date!
• Estimates range from 5-30 million
species on Earth.
– From the Convention on Biological
Diversity:
http://www.cbd.int/gti/taxonomy.shtml
• How do we keep track of them all?????
Classifying and Naming Species:
Taxonomy
– Each species is assigned a two-part name or binomial, consisting
of:
• The genus
• A name unique for each species
– The scientific name for humans is Homo sapiens (also H. sapiens),
a two part name, italicized and latinized, and with the first letter of
the genus capitalized.
Hierarchical Classification
– Species that are closely related are placed into the same genus.
Leopard (Panthera pardus)
Tiger (Panthera
tigris)
Lion (Panthera leo)
Jaguar (Panthera onca)
– The taxonomic hierarchy extends to
progressively broader categories of
classification
Species
Panthera
pardus
Genus
Panthera
Family
Felidae
Order
Carnivora
Leopard
(Panthera pardus)
Dumb Kids Play
Chess On Full
Guy’s Stomach
Class
Mammalia
Phylum
Chordata
Kingdom
Animalia
Domain
Eukarya
Taxonomy had a problem…
What testable criteria do we
use to classify species?
The Cladistic Revolution
– Cladistics is the scientific search for clades.
– A clade:
• Consists of an ancestral species and all its
descendants that share a set of evolutionarily novel
characteristics.
• Forms a distinct branch in the tree of life
– This is what Neil Shubin did in your extra credit
reading selection from his book “Your Inner Fish”
(2009).
Human Family Tree
from Shubin’s “Your Inner Fish” (2009)
Cladistics
in action
Humans are
multicellular
animals, that
have a bilateral
body plan,
skulls, hands
and feet, threeboned middle
ears, a bipedal
gait and large
brains.
Another example of cladistics…
Iguana
Outgroup
(reptile)
Duck-billed
platypus
Hair, mammary
glands
Gestation
Kangaroo
Ingroup
(mammals)
Beaver
Long gestation
Figure 14.23
Let’s use cladistics to look at the evolutionary relationships of the
immense biological diversity found on Earth
All organisms are made out of cells;
From your Flow of Matter model,
all cells have a plasma membrane,
DNA, and ribosomes; all cells are
made out of amino acids,
nucleotides, fatty acids and glycerol,
and monosaccharides!
Prokaryotes
Many metabolic processes evolved here.
Adaptation to an environment
filled with oxygen evolved.
Figure 15.10
All organisms made out
of eukaryotic cells
The Evolution of Eukaryotic Cells
The Endosymbiotic Model
The Diversity of Protists
Protozoans ingest food
Slime molds digest food extracellularly
A
malarial
parasite!
Unicellular algae:
photosynthetic
Multicellular algae: photosynthetic
Plants:
Eukaryotic multicellular
autotrophic (make their own
food through photosynthesis)
organisms adapted
to live on land
Comparing evolutionary
adaptations:
Living in water
vs
Living on land
Highlights of Plant Evolution
– The fossil record chronicles four major
periods of plant evolution.
Seedless vascular
plants
Bryophytes
Gymnosperms
Angiosperms
Get out Lab 08: Take 5 min
to read and share with class
major adaptations of each.
Team A - Bryophytes
Team B - Seedless vascular plants
Team C - Gymnosperms
Team D - Angiosperms
Angiosperm
life cycle
In the rest of Lab 08, we’ll discover
the many adaptations for spreading seeds
Figure 16.19
Fungi:
Eukaryotic unicellular and
multicellular heterotrophic
(rely on organic material for
food) organisms that digest
food externally and absorb
nutrients
Fungi
– Fungi are extremely important to
ecosystems because they decompose
and recycle organic materials.
Animals:
• Eukaryotic,
multicellular,
heterotrophic
organisms that obtain
nutrients by ingestion.
• Digest their food
within their bodies.
Animal Phylogeny
– To reconstruct
the evolutionary
history of animal
phyla,
researchers
must depend on
clues from the
fossil record,
comparative
anatomy,
embryology, and
molecular
biology.
– The first branch point is defined by the
presence of true tissues.
Sponge:
Lacks true tissues
– The second major evolutionary split is
based partly on body symmetry.
Cnidarians - true tissues and
radial symmetry
– Phylum Cnidaria
• Is characterized by the presence of body
tissues, radial symmetry, and tentacles with
stinging cells.
Thimble jellies - cause
disorder called Seabather’s
eruption
http://animals.jrank.org/pages/
1495/Jellyfish-ScyphozoaTHIMBLE-JELLY-Linucheunguiculata-SPECIESACCOUNTS.html
Flatworms - bilateral symmetry
– Phylum Platyhelminthes
• Is represented by the simplest bilateral animals.
• Includes free-living forms such as planarians
and parasitic forms such the tapeworm.
– Third, the evolution of body cavities led to
more complex animals.
– A body cavity
• Is a fluid-filled
space
separating the
digestive tract
from the outer
body wall.
• May be a
pseudocoelom
or a true
coelom.
Roundworms
– Roundworms exhibit two innovations not found
in flatworms:
• A complete digestive tract with two openings, a mouth
and an anus
• A body cavity, which in this case is a pseudocoelom
Annelids
– Phylum Annelida
• Includes worms with body segmentation.
• Have a true coelom
Check these out on your own!
Giant octopus attacks submarine
http://www.youtube.com/watch?v=9L
HTWmaOKpg
Molluscs
Cool mollusc movie! Scroll down
1/3rd way down
http://www.junglewalk.com/popup.as
p?type=v&AnimalVideoID=722
Purple clam opens
http://www.junglewalk.com/popup.as
p?type=v&AnimalVideoID=3220
Arthropod Diversity
– There are four main groups of arthropods:
• Arachnids, such as spiders, scorpions, ticks,
and mites
• Crustaceans, such as crabs, lobsters, crayfish,
shrimps, and barnacles
• Millipedes and centipedes
• Insects, most of which have a three-part body
Echinoderms
– Phylum Echinodermata
• Is named for the spiny surfaces of
the organisms.
• Includes sea stars, sand dollars, sea
urchins, and sea cucumbers.
Animal Phylogeny
– To reconstruct
the evolutionary
history of animal
phyla,
researchers
must depend on
clues from the
fossil record,
comparative
anatomy,
embryology, and
molecular
biology.
– Review your
reading guide
and the LONG
version of lecture
for a quick
summary
Humans belong
to this phylum
Characteristics of Chordates
– Members of the phylum Chordata all share four
key features:
•
•
•
•
A dorsal, hollow nerve cord
A notochord
Pharyngeal slits
A post-anal tail
– An
overview of
chordate
and
vertebrate
evolution
The Vertebrate Genealogy
– Vertebrates
• Are represented by mammals,
reptiles, amphibians, and fishes.
• Have unique features, including
the cranium and backbone.
– An
overview of
chordate
and
vertebrate
evolution
Tetrapods
– Tetrapods have 4 (tetra)
limbs (pods).
– Includes amphibians,
reptiles, and mammals
– Shows up in
Amphibians
• Exhibit a mixture of
aquatic and terrestrial
adaptations.
• Usually need water to
reproduce.
– An
overview of
chordate
and
vertebrate
evolution
Amniotes
• Amniotes adapted fluid-filled egg (in waterproof
shell or carried by mother) for living on land.
• Includes reptiles and mammals
• Reptiles (including birds!) and some mammals
lay amniotic eggs in which the embryo
develops.
– An
overview of
chordate
and
vertebrate
evolution
Getting closer to humans…
Mammals
– Two features are mammalian hallmarks:
• Hair
• Mammary glands that produce milk and nourish
the young
3 groups
of
mammals:
The Human Ancestry
Primates
are
eutherian
(placental)
mammals
Humans are primates
Some Common Misconceptions
– Our ancestors were
not chimpanzees or
any other modern
apes.
– Chimpanzees and
humans represent
two divergent
branches of the
anthropoid tree.
Common ancestor of chimps and humans;
now extinct
– Human evolution
• Is not a ladder with a series of steps leading
directly to Homo sapiens.
• Is more like a multi-branched bush than a
ladder.
– Upright posture and an enlarged brain
appeared at separate times during human
evolution.
– Fossil evidence pushes bipedalism in A.
afarensis back to at least 4 million years
ago.
The Genus Homo and the
Evolution of Inventive Minds
– Homo habilis,
“handy-man,”
• Had a larger brain.
• Probably made
stone tools.
– Homo erectus
• Was taller than H.
habilis.
• Had a larger brain.
• Gave rise to
Neanderthals.
The Origin and Dispersal of
Homo Sapiens
– The oldest known fossils of our own
species, H. sapiens,
• Were discovered in Ethiopia.
• Date from 160,000 to 195,000 years ago.
– Fossil evidence suggests that our species
emerged from Africa in one or more waves,
• Spreading first into Asia and then to Europe
and Australia.
Human Family Tree
from Shubin’s “Your Inner Fish” (2009)
Cladistics
in action
Humans are
eukaryotic
multicellular
animals, that
have a bilateral
body plan, skulls
(vertebrates),
hands and feet
(tetrapods),
three-boned
middle ears
(mammals), a
bipedal gait and
large brains.