APESUnit 03

Chapter 6Ecosystems and

Ecosystem Management

Basic Characteristics of Ecosystems

• Sustained life on Earth is a characteristic of ecosystems, not of individual organisms or populations

• Structure (two major parts)– Living (Ecological Communities)– Non-living

• Processes (two basic kinds)– Cycling of chemical elements– Flow of energy

• Change – Predictable – succession– Unpredictable change

Ecological Communities and Food Chains

• Ecological Communities are defined in two ways:– 1. A set of interacting

species that occur in the same place defined by the way they derive energy: Food chains, food webs, trophic levels (autotrophs)

– 2. A set of all species found in one area. EG. Zoo animals

Food Chains and Food Webs

• A Terrestrial Food Chain– Four trophic levels: – Example:

• Autotrophs• Herbivores• Carnivores • Decomposers

– People are omnivores

Food Chains and Food Webs Continued…

• An Oceanic Food Chain– Involve more species and tend to

have more tropic levels. See figure 6.6

• The Food Web of the Harp Seal– Shows how complex a real-life food

web truly is.

The Community Effect• Species interact directly (symbiosis &

competition) and indirectly• Community-level interactions

– Indirect interactions.• Keystone species

– Have large effects on it’s community or ecosystem

– Its removal changes the basic nature of the community

– See Sea Otter example figure 6.8. Sea otters influence the abundance of sea urchins

• Holistic View– An ecological community is more than the sum

of its parts.

How Do You Know When You Have Found an Ecosystem?

• Vary greatly in structural complexity.

• The watershed is a common, practical delineation.

• What is a watershed?• Common to all ecosystems

is energy flow and cycling of chemical elements.

Ecosystem Management

• Ecosystem management is the key to conservation of life on Earth, but it is difficult to know the exact limits of the system and is equally difficult to know all of the interactions that take place within it.

• If ecosystems cease to function we must supplement with our own actions.

• Must consider chemical cycling, energy flow, community-level interactions, and natural changes.

Chapter 7Biological Diversity

Biological Diversity and Biological Evolution

• Biological Diversity (biodiversity)– The variety of life-forms commonly

expressed as the number of species in an area

• Biological Evolution– The change in inherited characteristics of

a population from generation to generation– One of the features that distinguishes life

from everything else in the universe

Four Processes that Lead to Evolution

• Mutation

• Natural Selection

• Migration

• Genetic Shift

Mutation

• A chemical change in a DNA molecule• Affects the expressed characteristics

when cells or individual organisms reproduce

Natural Selection• 4 Characteristics:

– Genetic Variability– Environmental Variability– Differential Reproduction– Environmental Influence

• Species: – a group of individuals that

reproduce with each other and produce fertile offspring

Peppered Moth Example

• Originally White• Now more black than white• Causes

– Industrial Pollution• Soot covered trees

– Industrial Melanism

http://www.echalk.co.uk/Science/science.htm

Migration• Two new species evolve

from an original species due to isolation

• Ex: land bridge

Genetic Drift• Changes in the

frequency of a gene in a population due to chance

• Can be a problem for rare or endangered species

Basic Concepts of Biological Diversity

• Genetic Diversity• Habitat Diversity• Species Diversity• Species Richness• Species Evenness• Species Dominance

Species• A group of organisms that can reproduce and

produce fertile offspring.• Ubiquitous species

– Worldwide distribution– Overly common in an area

• Endemic species – Organisms unique to one place only.

• Indicator species– The first native organisms in an ecosystem, to

show the effects of environmental problems.

The Number of Species of Life on Earth• No one knows the exact

number• About 1.4 million species

have been identified and named

• Insects and plants make up moth of these species

• Number will increase

The Competitive Exclusion Principles

• 2 species that have exactly the same requirements cannot coexist in exactly the same habitat

• Ex) introduction of the gray squirrel into Great Britain

Professions and Places: The Ecological Niche and the Habitat

• Habitat: where a species lives

• Ecological Niche: a species profession

• The reason more species do not die out from competition is that they have developed a niche, and thus avoid competition

What is the effect of each species on the other?

Species Engage in 3 Basic Interactions

• 1. Competition• 2. Symbiosis• 3. Predation-Parasitism

• Each affect evolution, persistence of a species and the overall diversity of life

• Organisms have evolved together and therefore adjusted to one another

• Human interventions upset these adjustments

Symbiosis• The relationship between two

organisms that is beneficial to both and enhances each organisms chances of persisting– Mutualism, parasitism, commensalism

• Obligate symbionts: – a symbiotic relationship between two

organisms in which neither by themselves can exist without the other

– Ex) stomach of a reindeer

Chapter 8Biogeography

Part I

Why Were Introductions of New Species into Europe So Popular Long Ago?

• Biogeography: – The large scale

geographic pattern in the distribution of species, and the causes and history of this distribution

Wallace’s Realms: Biotic Provinces

• Realm: – Major biogeographic regions of Earth that

are based upon fundamental features of the plants and animals found in those regions

• Taxa: – Categories that identify groups of living

organisms based upon evolutionary relationships or similarity of characteristics (ex: species, families, orders)

• Biotic Provinces: – A geographical region (realm) inhabited by a

characteristic set of taxa, bounded by barriers that prevent the spread of those distinctive kinds of life to other regions.

The main biogeographic realms for animals are based on genetic factors .

The major vegetation realms are also based on genetic factors

Biomes

• A biome is a kind of ecosystem. Similar environments provide similar opportunities for life and similar constraints. – Rainforest– Grasslands– Desserts

Climate is the most important factor in determining the type of biome that will be found in an area

• The process by which species evolve in different places of times and, although they have different genetic heritages, develop similar external forms and structures as a result of adaptation to similar environments– Ex) shapes of sharks

Convergent Evolution

Divergent Evolution• Organisms with the same

ancestral genetic heritage migrate to different habitats and evolve into species with different external forms and structures, but continue to use the same type of habitats– Ex) Ostrich

Island Biogeography

• Theory of Island Biogeography– Islands have fewer species than continents– The smaller the island, the fewer the species

• Adaptive Radiation: – The process that occurs when a species

enters a new habitat that has unoccupied niches and evolves into a group of new species, each adapted to one of these niches.

• Ecological Island: – An area that is biologically isolated so that a

species occurring within the area rarely mixes with any other population of the same species

2. Small islands have higher rates of extinction.

1. Islands far from the mainland tend to have a lower rate of immigration

Which island would have the largest population based on 1 & 2?

Islands have fewer species than the mainland. This is a product of size as is seen on this graph.