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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.

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the complexity of life
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
Ecological Levels of Organization
  • 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
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
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
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
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
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.

Habitat and Niche
energy and nutrient flow through ecosystems
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.
the 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.

Levels of the Trophic Pyramid
food chain demonstrating trophic levels
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:

Food Chain vs. Food Web
marsh food web
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.
interspecies relationships
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.

Mutualistic Relationships
keystone species
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
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
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
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
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
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.