Transcript What is Life?-What is Out There?

Bios 101 PM
Biology of Populations and
Communities
• Dr. Alan Molumby
• [email protected]
• 6-2994
• 3084 SEL
• Office Hours MF 9, W at 11, or by appointment
What is Out There?
Reading: Freeman Chps. 1, 50 and 55
Biology is the study of life, but
what is life?
processes that define a living thing
• Organization and Information
• Need for an Energy Source
• Reproduction and Evolution
Organization and Information
• Living things are born and living things die. Although
true by definition, this underlies an essential propertythey are organized.
• So long as an organism maintains a given level of
organization, it is alive. When this organization
breaks down, it dies.
• Living things impose organization on nonliving matter
by growth, development, and reproduction.
• In death and decomposition, this organization breaks
down.
Homeostasis
• A critical aspect of life's organization is a
constant internal environment, called
homeostasis, which makes the complex
biochemical machinery of life possible.
Information
• Living things use a template to impose order on
nonliving things and to maintain order within
their own bodies.
• In all present-day living things, this template is
DNA (many viruses use RNA, but are they living?.)
• This template makes proteins, which are
responsible for our structure, function, and
metabolism-it is copied every time living things
reproduce.
DNA
• DNA is the prime substance of life itself (on
this planet, at least), it is as close to the
basis of life as we can get.
• DNA is the information template for life on
earth. Without DNA, living organisms
could not reproduce or function.
Need for and Energy Source
• All living things require constant input of
energy to survive.
• This is because life exists in a state of dynamic
equilibrium.
• A dynamic equilibrium is an organized system
that requires a constant input of energy to
maintain itself.
• Without input of energy, the organization
breaks down and death is imminent.
Humans are Heterotrophs
• Humans, like other animals, are heterotrophs.
We process energy that was originally captured by
other living things.
• Unlike plants, we cannot fix energy from sunlight,
nor can we fix energy by reducing hydrogen
sulfide these organisms are autotrophs and
chemoautotrophs respectively.)
• All of the energy we use to survive, and most of
the nutrients, were taken from another organism.
Reproduction and Evolution
• All living things are able to make copies of
themselves.
– It is in this area that the ambiguous nature of
viruses becomes apparent. A virus alone is
inert. It does not use energy and cannot
reproduce. In the presence of the right living
cells, however, viruses can direct the
production of million copies of themselves.
On Earth, types of living things fall into
(more or less) discrete categories called
“species”
• The definition of a species, and our reasons for
defining it that way, will come up several times during
this course.
• Basically, species are groups of organisms that
• 1-can interbreed and produce fertile offspring and/or
• 2-share a set of traits in common that distinguishes
them from other such groups and
• 3-is an evolutionary lineage that persists, ancestor to
descendant, over time
Question: Which of the following are inherent properties
of living things?
A)
B)
C)
D)
E)
Information
Sexual Reproduction
Need for an Energy Source
Respiration
A and C
How Many Species are Out
There?
• There are approximately 2 million described species on
Earth, estimates of the true number range from 5 to 30
million, with the number ranging as high as 100 million
if prokaryote “species” are recognized.
• So, most of what is out there remains undescribed.
• The process of describing a species is time-consuming, and demands
special skills which are in short supply.
– There is no central database of species, though several projects are
underway to change this.
– There is also an attempt to create a central database of phylogenetic
information.
• There are difficulties with the species concept; cryptic species, species
named more than once, and polymorphic species
– As a result, only a small fraction of species are named and described,
some existing species have been named several times.
• Some taxa are known much better than
others.
– For example, birds, mammals, flowering plants,
and butterflies are well known,.
– Most species in these groups have been
described and named.
• Most insect groups, such as the chalcidoids
and beetles, are less well-known, but
becoming much better-understood.
– Only a fraction of the insects have a name and a
description.
• For some groups, including most
microorganisms, we are only beginning to
comprehend their true diversity.
Above is a chalcidoid, named and described,
Below are microbes from a Greenland glacier,
no formal description yet
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Group
No. of described species
Prokaryotes
4,760
Fungi
46,983
Algae
26,900
Bryophytes
17,000
Gymnosperms
750
This is what
Angiosperms
250,000
we have described
Protozoans
30,800
Sponges
5,000
so far,
Corals and jellyfish
9,000
note the large number
Roundworms and earthworms
24,000
of insects
Crustaceans
38,000
Insects
751,000
Other arthropods and minor invertebrates 132,461
Mollusks
50,000
Echinoderms
6,100
Fishes (teleosts)
19,056
Amphibians
4,184
Reptiles
6,300
Birds
9,198
Mammals
4,170
Total species
1,435,662
From E.O Wilson’s Biodiversity
This figure is fairly old, the numbers of described species
In each group have increased, but the proportions have remained
fairly similar.
Clicker Question: Which of the following
taxonomic groups has the LARGEST
proportion of UNDESCRIBED species?
A) Birds B) Butterflies C) Mice
D) Beetles
E) Bats
The Old Classification
This “five kingdom” scheme of classification replaced the old
animal kingdom vs. plant kingdom scheme in the 1970’s. It is an
excellent grouping of organisms based on their characteristics, but
it does not reflect evolution very well.
The “Tree Within a Tree” Phenomenon
• Very often, groups of organisms appear to be similar
because they share a great many “primitive”
characteristics.
– This similarity is superficial, however, because very
different organisms often possess the ancestral state for
many characteristics, despite a great deal of evolution in
different directions.
– Best way to define groups is based upon synapomorphies,
new traits that arise in the common ancestor of a lineage and
are inherited by the members
– When organisms are classified this way, it becomes apparent
that most of the organisms that seem familiar to us are a
cluster of branches within a much larger tree.
• An important adaptation has enabled diversification
– This pattern is repeated many times in evolution.
From paleos.com
New ideas on the tree of life
Modern methods of sequencing
DNA, and a modern approach
to systematics allows a greater
understanding of the true
“tree of life”
The tree on the left, based upon
ribosomal RNA, which is very
evolutionarily conservative
endicates that there are three major
“domains” of living things.
The prokaryote archaea are closer
To eukaryotes than the bacteria.
From wikipedia.com
• This is a reasonably current universal phylogeny of living things.
• As we know more, the picture changes.
• To surf the tree of life, go to http://www.tolweb.org
Some Highlights in the Tree of
Life
http://www.ucmp.berkeley.edu/archaea/archaea.html
Prokaryotes
• “Prokaryotes” are the most ancient, most
abundant, and most metabolically diverse
organisms.
– This term describes a state of organization (no
nucleus) rather than a taxonomic group.
• Prokaryotes include the:
– Bacteria
– Archaea
Bacteria
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Proteobacteria
Cyanobacteria
Gram-Positive Bacteria
Chlamydias
Spirochetes
Proteobacteria
• The proteobacteria are a large and diverse group that
includes photoautotrophs, chemoautotrophs, and
heterotrophs.
– There is no taxonomic divide between “good” bacteria,
those that are essential to the functioning of the
biosphere, and “bad” bacteria, those that can kill us.
• Pathogenic bacteria occur within many different groups.
• On the basis of 16s RNA, they can be broken down
into five basic groups
– Alpha
Beta Gamma
Delta
Epsilon
www.biology.ed.ac.uk/.../microbes/myxococc.htm
Among the delta
proteobacteria are
the myxobacteria,
interesting gliding
bacteria that
produce “fruiting
bodies” under
conditions of
starvation.
Myxobacteria live
in the soil, and
“glide” along
solid surfaces via
a polysaccharide
slime.
• Among the alpha
proteobacteria are the
ancestors of
mitochondria.
• Also included are
Rhizobium species that
live in the roots of
plants,
• and the
rickettsias, tiny
pathogens that
live within the
cells of animals
bioinfo.bact.wisc.edu/.../Effects.html
Spirochetes
• These are among the
most distinctive
bacteria
• they move by a
spiraling corkscrew
motion.
• They can be free
living or parasitic.
• Syphilis and Lyme’s
disease are caused
by spirochetes
Archaea
• Although we know very little about them, the archaea are some
of the most abundant, and important, organisms on the planet.
– The group is very ancient-some bear a striking resemblance
to fossils dated at more than two billion years old and many
exploit ecological niches that were probably more important
billions of years ago.
– Though the majority live in ordinary habitats, the group
includes many exptremophiles.
– These include;
• methanogens-live in anerobic conditions and break down
methane
• extreme thermophiles-live in incredibly hot environments
• extreme halophiles-live in extremely salty environments
Eukaryotes
• Eukaryotes are much more diverse than was
previously thought.
– Modern studies of eukaryote taxonomy indicate
there are probably between 11 and 20 eukaryote
kingdoms, rather than simply plants, animals,
fungi, and protists. These kingdoms include
many groups formerly classed simply as
“protists”, such as Diplomonads and
Parabasalids.
From Baldauf, SL Science, 2003, Jun 13 1703-6
Some Kingdoms of Eukarya
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Euglenoids
Alveolates
Discicristates
“Ameboid” protists
Ophistokonts
– This includes us, by the way
“Protists”
• “Protists” are simply eukaryotes that are
unicellular for most of their life cycle.
– There are many groups of distantly related protists,
which are now thought of as “kingdoms” in their own
right.
– Several groups have independently acquired
photosynthesis, and become “algae”, others have
evolved multicellularity.
• One group of multicellular protists evolved into animals.
• Another lineage evolved into fungi.
• There are several multicellular lineages, such as slime
molds, that neither plant nor animal nor fungi.
Fungi
• Fungi are a kingdom of organisms that
includes decomposers, parasites, and
mutualisms.
• There are four major groups;
• Chrytridomycots
• Zygomycots
• Ascomycots
• Basidiomycots
EO Wilson’s Biodiversity again
Viridiplantae
• This group includes the green plants and the
basal “bush” from which they originated.
They have chlorophyls a and b, as well as
certain other distinguishing characteristics.
• Green Algae-Chlorophytes
• Charophytes
• Plants
True Plants
• These include several
groups of multicellular,
terrestrial
photosynthesizers,
including
• Bryophytes-mosses, etc.
• Pteridophytes-ferns.
• Gymnosperms
• Angiosperms-flowering
plants
Animals
• Animals are a true lineage of
multicellular organisms
evolved from one line of
protists (probably resembling
a group called the
choanocytes).
• They have evolved many
different body plans, each of
which represents a phylum.
• There are about 30 presentday animal phyla, there were
probably more in the distant
past.
Organisms Create
Habitats for Other
Organisms.
Many individuals of
a single species
are called a
biological
population
Populations of
organisms tend
to assemble into
biological
communities
Biodiversity
• Genetic Diversity within Populations
– Diversity of Populations Within Species
• Number of Species
– in a given habitat (alpha diversity)
– accounting for the diversity of habitats, and the
change in species from one habitat to the next
(beta)
– total number of species (gamma)
• Communities and Ecosystems
Question: Which of the following organisms is NOT
a eukaryote?
A) A spirochete (Treponema sp.)
B) Euglena sp.
C) A frog (Hyla sp.)
D) A dandelion (Taxacum sp.)
E) All of the above are eukaryotes.
Ecology and Evolution
• The sciences of ecology and evolutionary biology are often
taught together, and at many universities, the two sciences are
part of a single academic department.
• This is because the mechanisms that drive evolution are
fundamentally ecological, and the participants in ecological
interactions are products of evolution.
• The two subject areas interrelate so extensively that some areas
of research, such as life history evolution, biogeography,
coevolution, and macroevolution, are inextricably entwined in
both sciences.
• They provide an answer to the question of why there are so
many species are out there, as well as an answer to the question
of why they take the forms they do.
Example: Pollination Syndromes in Flowers
• Naturalists have long observed that flowering plants, in a wide variety of taxa
convergently evolve characteristics which match one of several “pollination
syndromes.”
– The same pollination syndromes evolve in widely disparate types of plants.
Likewise, widely disparate types of pollinators will evolve to exploit these
syndromes.
• These “syndromes” are discrete sets of floral, nectar, and pollen characteristics
that match the sensory abilities, metabolism, and biology of their pollinators,
and act to ensure efficient pollination by manipulating the behavior of the
pollinator.
– Pollinators evolve in response to these floral characteristics, the result being a
coevolutionary interaction that intensifies the relationship.
– Example; A flower evolves a long corolla to ensure that hawkmoth visitors must
reach deeply into a flower in order to reach the nectar “reward” provided by the
flower, thus placing their faces in the appropriate location to receive pollen.
– The hawkmoths respond by evolving longer tongues, to enable them to more easily
reach the nectaries of the flowers.
– This, in turn, places selective pressure on the flowers, and intensifies the
relationship. The longer nectary, in turn, makes it nearly impossible for longtongued bees to visit the flowers, and drives the system toward an obligate
mutualism, rather than a looser, facultative mutualism.
• Charles Darwin was fascinated by
pollinators.
• Upon examination of a Madagascar
Star orchid, (Angraecum sesquipedale),
which has a nectar tube over ten inches
long, he famously predicted that there
must be a hawkmoth with a tongue ten
inches long to pollinate it.
• At the time, only the orchid had been
discovered.
• 40 years later, the moth was discovered,
Xanthophan morgani praedicta, now
called Darwin’s hawkmoth.
• In this particular scenario, part of the
selective pressure driving the system is
that the moths are safer from predatory
spiders, but less effective as pollinators,
if they never get too close to the
flowers as they feed.
• In addition to the evolutionary consequences of these syndromes,
they have ecological aspects as well.
• Under some circumstances, flowers effectively “compete” for
pollinators. Flowers that are more conspicuous, and offer greater
rewards, get more pollinators, but since these syndromes restrict
the types of pollinators that can visit flowers, they restrict the
scope of competition.
• Pollinators very often compete for nectar, and for pollen.
Specialist pollinators that visit only one type of flower are
sometimes protected from interspecific competition (sometimes
not, pollinator specialization does not imply that the flower can
only receive one type of visitor), but at the cost of extreme
ecological specialization.
• This specialization causes the pollinator to evolve behavior and
life history to match the appearance of the flowers they pollinate.
• Other pollinators are “generalists”, able to visit a wide variety of
flowers within their own pollination syndrome.
• For instance, the squash
bee, Peponapis pruinosa
feeds on the nectar and
pollen of squash,
exclusively. Though other
bees visit squash, it is the
most effective pollinator.
Males hide in squash
flowers day and night,
waiting for females to
mate with in the early
mornings as they forage
for pollen.
The abundance of this
pollinator makes squash
and pumpkins easy to
cultivate, even though
most gardeners do not
know the squash bee
exists. Squash bees time
their emergence to late
summer.
• The most common pollination syndromes:
• Flies and generalists-open flowers, easy to reach pollen, accessible nectaries. Large
amounts of pollen because most of the visitors are after pollen. Usually early spring.
• Long-tongued bees-moderately long corollas, flowers are white, blue, yellow, infrared,
small amounts of sucrose-concentrated nectar, sometimes a “landing pad” for bees, and
sometimes petals that must be pushed apart for the bee to reach the nectar. Scented
flowers, open in daytime. Sticky pollen that bees can easily collect and transport, nectar
guides.
• Short-tongued bees-white, yellow, infrared flowers, short corollas with easily available
pollen, no special tricks with petals, but usually asymmetric. Scented flowers open in
daytime. Sticky pollen. Sucrose-dominated nectar in variable amounts.
• Bumblebees, Amigillia bees-as with long-tongued bee flowers, but bee must hang
upside and buzz to release pollen.
• Hawkmoths-very long corollas that effectively force the moth to push its face into the
stamens in order to reach reward (moths are not after pollen, so they must be tricked
into transporting it), white flowers that are heavily scented and open at night, small
amounts of concentrated nectar.
• Butterflies-as above, but flowers run more to the pink or lavender and have a landing
platform.
• Hummingbirds-red flowers (only vertebrates see that color well) with very long corollas
and large amounts of dilute nectar, flowers open in daytime, and bird is forced to push
face into stamens in order to feed. No scent.
• Bats-large amounts of dusty pollen that will stick to mammal hairs, very big flowers tha
bats can reach into with their faces, open at night,
• Beetles-flowers smell like carrion and offer large amounts of pollen
• African baobabbat pollinated.
• Day-flying sphinx
moth nectaring on
African vervain.
• Syrphid fly on a
crocus flower.
• Clicker Question
• If a flower smells like rotten meat, is not colorful,
and offers large amounts of pollen, what should
pollinate it?
A. Bats
B. Bees
C. Hummingbirds
D. Butterflies
E. Carrion beetles