Chapter 7 - Biological Diversity and Biogeography

Case StudyPurple Loosestrife

What is biological evolution?• It’s the change in inherited characteristics

of a population from generation to generation.

• What are some process that lead to biological evolution?

• 1.• 2.• 3.• 4.• 5.

Mutations may:

• Natural SelectionRelies on variation of individuals within a species. Genetic diversity is key!

Those orgs with traits that make them better fit or adapted survive well, reproduce more and pass these helpful traits on to their offspring.

Peppered moth = classic example.

Photos by Ken Miller

• Speciation (evolution of a new species)1. Geographic isolation of two populations of the same species

2. They each evolve separately

3. Eventually differences accumulate

Reproductive isolation can occur due to mutations too.

MigrationDuring migration different selective pressures may be encountered.

Populations may become separated Genetic DriftChanges in gene frequency of a population due to chance - not due to being better adapted

May greatly impact small populations Dangerous for rare and endangered species

Extreme hunting left only 20 Few individuals left – why?

Basic Concepts of Biodiversity

• 3 major concepts:1. Genetic diversity

2. Habitat diversity:

3. Species diversity: a. Species richness –

b. Species evenness –

c. Species dominance -

Hwk• Shannon-Weiner Biodiversity Index• Read and do sample problems.• Show all work and solve for H’• Also: Calculate Evenness for each problem:– Evenness:– Formula = H’ / ln S– S = number of different species – (Absolute evenness = 1)

Hwk

• Pre-lab work for Wed.• Answer pre-lab questions.• #1 in INB.• #2 and 3 become your hypothesis, under

purpose on title pg.• Calculate S-W biodiversity index for both

pictures (fig. 7.4) on page 123.• Solve for H’ and Evenness.• Show all work.

• Species habitat terms: exotic = introduced

endemic = native

cosmopolitan - very broad distribution but need similar habitat

ubiquitous = found almost everywhere even very different habitats

How many species on Earth?

• Uncertain• Prior to fogging study:

Range = 1 - 3 million

• After study: 10 -100 million!

Interactions Between Species

• 3 kinds:1. Competition: negative for both

2. Symbiosis: both benefit• It is very common; exists amongst most

plants and animals

• 3. Predation - parasitism: positive for one and negative for the other

• Exclusion Dominance and Diversity: The

Competitive Principle• Competitive exclusion = 2 species with exact

same requirements cannot coexist in the same habitat. They will compete and the more fit one will win out and persist

© 2003 John Wiley and Sons Publishers

Fig 7.6 A classical experiment with flour beetles.

• Niche: how species co-exist.• A habitat is where an org lives as compared to

what it does to survive, which is its’ ecological niche

• Species that require the same resources can coexist only if they can utilize them under different env. conditions (different ecological niches).

• Species that require the same resources can coexist only if they can utilize them under different env. conditions (different ecological niches).

• Niches can be measured:• The range of niche a species will occupy with no

competitor is called its’ fundamental niche

• The range in which it actually lives, if it is having to compete, is called its’ realized niche

© 2003 John Wiley and Sons Publishers

Fig 7.7 The occurrence of freshwater flatworms in cold mountain streams in Great Britain.

Environmental Factors That Influence Diversity!!

• Diversity varies from place to place• Generally, greater in lower latitudes

• Ecological gradient: the change in relative abundance of a species over an area (ie: change in elevation in the mtns.)

© 2003 John Wiley and Sons Publishers

Fig 7.10 Change in the relative abundance of a species over an area or a distance is referred to as an ecological gradient.

• Factors that increase or decrease diversity:• Increase diversity:

1. Physically diverse habitat

2. Moderate disturbance

3. Small variation in env. conditions

4. High diversity at one trophic level increases diversity of another level

• Decrease diversity1. Environmental stress

2. Extreme environmental conditions

3. Severe limitation of an essential resource

4. Extreme disturbance

5. Recent exotic species

6. Geographic isolation (island effect)

• Humans greatly affect diversity :

– Development and industry

– Favoring one species over another

– Manipulating environments

• Species diversity in an area may change over time, seasons, decades, centuries...

The Geography of Life• The kinds and numbers of species varies

greatly from place to place. These large-scale global patterns are called biogeography

• Biotic Provinces• Six “realms” were identified in 1876 based

on the types of animals found there:• (Remember: classification of orgs are based

on evolutionary relationships or similar characteristics)

© 2003 John Wiley and Sons Publishers

Fig 8.3 The major vegetation realms are also based on genetic factors.

• Continental drift explains the origin of these provinces as land masses periodically unified (genetic mix and spread of species) and then separated (isolation and speciation)

• Biomes:• Each continent has diverse climates and habitats

so diversity of species is high

• Biome = a kind of ecosystem

• Similar environmental conditions (selective pressures) lead to evolution of orgs similar in form and function but not genetic heritage or internal make-up.

© 2003 John Wiley and Sons Publishers

Fig 8.13 Global distribution of the major land biomes.

• Divergent evolution occurs when a pop. is separated and evolves in isolation from main groups, often under different selective pressures. They have common ancestry and retain some common characteristics of their ancestors. (ex: marine mammals)

© 2003 John Wiley and Sons Publishers

Fig 8.10 Evolutionary divergence among honeycreepers in Hawaii.

• Island Biogeography– Generally observe adaptive radiation: species

evolve by divergent evolution as they separate into smaller groups, often on different islands, each adapting to a more specialized role (niche)

– Species diversity and islands:

© 2003 John Wiley and Sons Publishers

Fig 8.11 Idealized relation of an island’s size, distance from the mainland, and number of species. Pg 138