The Complexity of Life
Heather Markham
ID# 53734534
Prof. White
December 4, 2002
The Complexity of Life
• To get a good understanding of the complexity
of life, one must understand the complicated
networks and systems at work in nature that
make it possible for life to exist.
• This presentation will give you a background
in ecology so that you will see the depth of
intricateness necessary for nature to sustain
life.
Ecological Levels of
Organization
•
•
1.
2.
3.
4.
These levels were established so scientists could
map out the complex interconnecting networks
in nature
The four ecological levels of organization are:
Species
Population
Communities
Ecosystems
Species
• Collectively, a group of individual organisms that
are capable of interbreeding under natural
conditions are referred to as a species.
• Organisms of the same species can have
different physical and/or behavioral
characteristics.
• For example, consider the human species (Homo
sapiens). Humans exhibit considerable variety in
both physical and behavioral characteristics. This
same type of variety also occurs in plant and
animal species.
Population
• A group of individuals of the same species that
occupy a particular area over a given interval of
time are referred to as a population.
• Take note that a population does not necessarily
include all the individual members of a species and
there can be multiple populations for each species.
• For example, the raccoon species is spread all over
North America from the East coast to the West
coast. The East coast population of raccoon is
different from the West coast population in that
the East coast raccoons tend to have thicker fur to
deal with the cold.
Communities
• Populations of various species living in the same
area, having a multitude of interactions and
dependencies, are referred to as a community.
• Although the members of a community are not
static and may be seasonal, the interaction
between the flora and the fauna allow nature to
exist and thrive.
• Communities can change over long periods of time
in a process known as ecological succession.
During succession, some species are replaced over
time by other species as new environmental
conditions develop.
Ecosystems
• The community and the abiotic (or non-living)
elements of a particular area function as a unit called
the ecosystem.
• Ecosystems are typically classified by ecologists as
aquatic or terrestrial ecosystems. An example or a
terrestrial ecosystem would be a N. American
coniferous forest or dessert. An aquatic ecosystem
could be a river or pond.
• Ecosystem types vary with location based on climatic,
topographical, geological, chemical, and biotic
factors. It seems that ecosystems are related to
latitude.
• Ecosystems also vary in size. For example a pond vs.
a lake.
Small World Idea
• The concept of a “Small World” is based on the
idea of Mark Granovetter.
• The “Small World” phenomena is the idea that
even though life seems so diverse it is actually
very interconnected, so much that affecting one
relationship can dramatically affect other loosely
tied relationships.
• The idea of “Small Worlds” can be applied to any
complex system of interaction, like in nature
where relationships between different species of
animals are typically based on food and survival.
Habitat and Niche
• The term habitat refers
to the place ( or type of
place) where an
organism most
commonly resides. The
habitat allows the factors
necessary for the
survival of species and
populations.
• An example of a habitat
could be the rocky
hillside in which the
Diamondback rattlesnake
make it’s home.
• The concept of an
ecological niche is used in
explaining how species
coexist in the same
community. An Ecological
niche is comprised of all
biotic as well as abiotic
factors necessary for an
individual to survive in
their habitat.
• A Niche is sometimes
thought of as the "role" an
organism fulfills in the
ecosystem. It is the
adaptive role that the
species has in a habitat.
This includes it’s behavior
and interaction with other
species.
Energy and Nutrient Flow
Through Ecosystems
• The complexity and interconnectedness of nature
that makes life possible is astounding.
• We’re now going to look at the Trophic Pyramid
that relates to the food web. It shows the four
levels of predation within nature. It directly
addresses the relationships between species on
different levels as well as indirectly address the
relationships between species on the same trophic
level.
Trophic Pyramid
3D Trophic Pyramid
The Trophic Pyramid
•The first level of primary producers
limits the available biomass and
subsequently limits the size of upper
levels.
•Only ten percent (10%) of the total
energy of that level will get passed up to
the next level, all the rest of the energy
if lost to respiration (which is the energy
needed to stay alive and function).
Levels of the Trophic Pyramid
• Primary Producers:
Primary Producers are the
plants that turn the sun’s
energy into energy usable
to animals.
• Primary Consumers:
Primary Consumers (the
second level) are
herbivores that eat the
plant life from the first
level.
• Secondary Consumers:
Secondary consumers can
be carnivores or omnivores
and pray on both the first
and second level.
• Terciary Consumers:
Terciary consumers tend to
be omnivores that typically
eat more meat than plants.
They are considered the top
predators and only a stable,
diverse environment can
support them.
Food Chain Demonstrating
Trophic Levels
This food chain shows 5 trophic levels. The
more biodiverse the environment the more
trophic levels there are.
Food Chain vs. Food Web
Food Chain
The idea of a food chain
has become outdated with
the increasing knowledge
of the interconnectedness
of the complex system of
nature. A food chain does
not represent all the other
things the animals might
eat. In turn, the food chain
just does not have the
complexity needed to
understand predation.
Food Web
A more realistic
representation of
feeding relationships in
an ecosystem is a food
web. A food web
demonstrates the
multiple links between
species. Here is a
diagram of an aquatic
food web demonstrating
the trophic levels:
Marsh Food Web
• It should be noted many animals fit into more than one trophic level
depending on how you look at it. Also, the highest level can prey on all
lower trophic levels.
Aquatic Food Web
General Energy and Nutrient
Transfer System
Interspecies Relationships
• The basic concept of cross species interaction is
the predator-prey relationship where one species
(at a higher trophic level than the other-typically)
eats another species.
• Parasitism is where one species benefits at the cost
of the other. This kind of relationship is commonly
found in insects.
• Not all cross species relationships are based on
who eats whom; some relationships are based on
two species working together.
• There are two types of mutualistic interaction:
symbiotic interaction or nonsymbiotic interaction.
Mutualistic Relationships
Symbiotic Interaction
• A symbiotic relationship is
where the species interact
physically and their
relationship is biologically
essential for both of their
survival.
• For example, Mycorrhizae,
which is a fungus, lives on
the root of a tree extracting
nutrients from the soil
allowing the tree can
survive, the Mycorrhizae in
turn is provided with a
habitat and nutrition.
Nonsymbiotic Interaction
• A nonsymbiotic
relationship is where the
mutualists live independent
lives yet cannot survive
without each other.
• For example, pollinating
insects like bees and some
flowering plants work
together. The bees feed off
the flowers and in turn
collect pollen on
themselves that they
deposit on another flower,
pollinating it.
Keystone Species
• Any change in local populations of
keystone species can have significant
impacts on the functioning of ecosystem
processes, predatory relationships, and
overall long-term stability.
• The role of keystone species is crucial for
the balanced functioning of the ecosystem.
• A classic example of a keystone species is
the sea otter (Enhydra lutris).
Barabasi’s Quote
• As Albert-Laszlo Barabasi states it “Ecologists believe that
the hubs of the food webs are the keystone species of an
ecosystem, paramount in maintaining the ecosystems
stability…Hubs are special they dominate the fields of all
networks in which they are present, making them look like
small worlds…hubs are not rare accidents of our interlinked
universe. Instead they follow strict mathematical laws whose
ubiquity and reach challenge us to think very differently
about networks” (Barabasi, p. 64).
• Here Barabasi is looking at ecosystems as complex networks
where keystone species are considered hubs due to their
unproportionately large amount of “connecters” or links to
other species.
• This leads to the idea of the “rich get richer.” The “rich get
richer” phenomenon naturally leads to power law
distributions where the rich (or in this case the hubs) get
richer (more connecting links) increasing their influence on
the network (ecosystem).
Types of Adaptations
• There are three types of adaptations: genetic,
developmental and acclamatory.
• Acclamatory adaptations are short term and reversible.
They are your body’s way of adapting to different weather
conditions.
• Developmental adaptations occur during the development
of the organism where the phenotype is changed.
• Genetic adaptations are changes that take place across
generations. The change occurs in the genotype of the
organism where beneficial genes are passed on to the next
generation.
• One more type of adaptation (that only occurs in humans)
is cultural adaptation. In cultural adaptation people use
technology (clothes, housing, heaters…) to deal with their
environment.
Evolution
• The basic idea of evolution came from Charles
Darwin who was inspired by Malthus.
• Charles Darwin’s idea was actually two fold,
dealing with both specific and general evolution.
• General evolution refers to the increasing
complexity of life over time where evolution
occurs by natural selection.
• Specific evolution refers to the adaptation of a
particular species to a specific environment across
generations.
Extinction
• For those who could not adapt and evolve to their
ever-changing environment extinction was in their
future.
• Van Valen suggested that “constant extinction
probability would result from a constantly changing
biotic community, in which species continually adapt
to each other’s changes” (Sole & Goodwin, p. 254).
• Extinction rates follow a power law distribution that
obvious when looking at the history of the Earth. The
network like structure of ecosystems can sometimes
lead to unlikely events like the cataclysmic extinction
of the dinosaurs.
• In the long run it is the network and the emergent
properties arising from network dynamics that
determine the collective behavior of ecologies.
Abiotic Systems
• When looking at the interconnectedness in
the network like structure of nature one
must consider the abiotic factors of the
environment that allow life to exist.
• The main biochemical cycles on Earth that
affect life’s very existence are the
hydrologic cycle, the carbon cycle, and the
nitrogen cycle.
The Hydrologic Cycle
The Carbon Cycle
The Nitrogen Cycle