2.1 Biological diversity includes genetic, species, and community/ecosystem diversity
Species diversity
Species are defined commonly using two concepts
1. biological species concept
-group of individuals that breed among themselves but not among other
groups
-used by evolutionary biologists and works well for birds and mammals
that are well known and have reproductive data
Ex meadowlarks Fig. 2.3
2. morphological species concept
-group of individuals morphologically, physiologically, or biochemically
distinct from other groups
-most commonly used by taxonomists
1. List two species observed on the fieldtrip and explain how each
concept applies.
Fig. 2.3 The w. and e. meadowlarks are distinct species, though morphologically similar.
2.2 (A) Botanist collecting plant specimens; (B) Natural history collections such as at Harvard
2. List a plant and animal species from the field trip and use the taxonomic categories except
order and family to classify the observed organisms.
Taxonomy is the science of classifying living things into a hierarchial system
Kingdom - Monera (eu- and archeabacteria), protista, fungi, plants, animals)
Phylum or Division - Magnoliophyta and Chordata
Class - Magnoliopsida (dicots) and Liliopsida (monocots) and fishes (Agnatha,
Chondryichthyes, Osteichthyes), amphibians, reptiles, Aves (birds), as well as mammals
Order
Family
Genus
Species = genus + species epithet
- binomial nomenclature developed by Linneaus Ex. Homo sapiens
Box 2.1 Blackburnian warblers are related to more and more other animals at successively higher
levels of taxonomic organization
Difficulties in distinguishing species
1) species concept and problems with taxonomy
2) varietal or subspecific variation
Ex. breeds of dogs all belong to one species by a biological definition
-difficult to distinguish variation within a single species from that between
closely related species Ex. threatened (ivory tusks) African elephant -- Is it a
single widespread species or three separate species/subspecies that occur in
desert, forest, and savanna?
3. Did you encounter any varieties or subspecies on the fieldtrip? What are the
differences in the two categories?
2.3 Dogs are all one species and readily interbreed
There are about 600,000 African elephants, and between 30,000 and 50,000
Asian elephants. The Africans dropped by 50%, from 1.3 millions to 600
000, between 1979 and 1989, because of poaching. About 8 elephants an
hour (70,000/year) were poached during this period, until the CITES Ivory
ban 1989. The CITES (Convention of International Trade In Endangered
Species) regard both species as threatened.
Indian (Elephas maximus)
small ears
one lobe at trunk tip
five toenails
India and SE Asia
African (Loxodonta africana)
large ears
two lobes at trunk tip
four toenails
widespread in S 2/3 Africa
-some advocate dividing it up into a
savannah, forest, and desert species
Difficulties in distinguishing species (cont.)
3) hybrids
-often sterile because chromosomes cannot pair in metaphase I
-if fertile they violate the biological species concept
-common in plant species
-few remaining red wolves (Canis rufus) may all be hybrids with coyotes (Canis latrans)
and may lose its status as endangered and go extinct due to hybridization
red (Canis rufus)
grey (C. lupus)
coyote (C. latrans)
medium
large
small (1/2 size of red wolf)
more slender face
SEUSA
Canada
widespread
Alaska
Minnesota
4. Red wolves occurred in the areas we are in for the fieldtrip, what happened to them?
Figure 2.4 The hybrid tiger salamander (left) is larger than its parent species (California tiger
salamander (right) (an endangered species) and introduced Barred Tiger salamanders) and is
increasing in abundance
Origin of new species
1. gradual speciation or phyletic evolution
-gradual transformation into another species
-first described by Charles Darwin and Alfred Wallace (Darwin, C. 1859. On the
Origin of Species)
Read Pgs. 29-30 of text on mountain rabbits in Canada
-usually involves a geographic barrier = allopatric speciation
Ex. E and W species of plants and animals in North America
2. rapid speciation
-often occurs on islands through a process called adaptive radiation - local adaptation
and subsequent speciation Ex. 1) mouthparts of insects, 2) Honeycreeper family of
birds originated in Hawaii 10s of 1000s of years ago from a single pair of birds
5. How might Fall and Summer species of grasshoppers, possibly observed on the
field trip have diverged into new species?
6. For what kinds of organisms might the Colorado River serve as a geographic
barrier?
7. Discuss adaptive radiation in insects, which are an important part of the river
fauna?
2.5 The Hawaiian honeycreeper family is a spectacular example of adaptive radiation
Rapid speciation may occur in a single generation in the same geographic area (sympatric)
because of polyploidy
Ex.
Parents
Gametes
10 chromosomes
5 chromosomes
X
X
Offspring
= 9 chromosomes that do not pair producing a sterile hybrid
Parents
Unreduced gametes
10 chromosomes
10 chromosomes
Offspring
= 18 chromosomes that pair producing a fertile polyploid that is
intermediate in morphology and reproductively isolated from
parents
X
X
8 chrom.
4 chrom.
8 chrom.
8 chrom.
-common mode of speciation in plants and invertebrates
8. Species of domestic peanut that occur in the field trip region are tetraploids with 40
chromosomes that come from two wild species. Explain how this could have
occurred.
Species arise all the time but today species extinction is about 100-1000X
faster than speciation. Why?
1) much of earth’s surface is occupied by people
2) many of species threatened with extinction are the sole remaining
representative of their genus and family Ex. coelacanth, giant panda,
ginkgo
3) existing protected areas and national parks may be too small for speciation
9. Colorado Bend State Park is over 5000 acres, is this large enough for
speciation of vertebrates and angiosperms?
10. Is the Texas horned lizard the sole representative of their genus or
family? How does this affect its conservation status?
2.6 Certain groups of organisms apparently need a minimum area in order to undergo the process
of speciation
Measuring Species Diversity
-no simple relationship between diversity and stability of communities
-many diversity indices are used and most incorporate two ideas
1) richness - number of species in a community
2) evenness - number of individuals of each species in a community
-mathematical indices of biodiversity have been developed to describe three
different geographic scales
1) alpha (local) diversity = richness/small (local) area
2) gamma (total) diversity = richness/region
3) beta diversity = gamma diversity/ average alpha diversity
-represents variability of species composition along an environmental or
geographical gradient
-indicates whether each part of a region has a more distinct assemblage of
species than another part. Low beta=local diversity important whereas
high beta=regional diversity more important
11. Explain how these would be used in regard to our bottomland tree
species?
2.7 Biodiversity indexes for three regions, each with three mountains
Genetic diversity
-observable units are populations- group of individuals in same place and
time that mate and produce offspring
-individuals within a population are genetically different from each other.
They have different forms of genes or alleles that arise from mutations
in DNA. All the genes and alleles in a population = gene pool
2.8 The phenotype of an individual is determined by its genotype and by the environment
2.9 Genetic variation at the population and individual.
Genetic variation is due to:
1) Mutation
a. point- one nucleotide is substituted for another
b. frameshift- a nucleotide is added or deleted
2) meiosis and recombination during sexual reproduction
a. crossing over in Prophase I
b. independent assortment in Metaphase I
c. recombination of two genotypes during fertilization
-most mating occurs within populations but individuals occasionally move
from one population to another allowing for the transfer of new alleles =
gene flow
12. Explain how mutation,
13. as well as meiosis and recombination could change an organism
observed on the field trip?
Amount of genetic variation is measured by:
1) number of polymorphic genes- genes with more than one allele
Ex. 1a1a, 1b1b, 1c1c
2) number of heterozygotes that result from polymorphisms
Ex. 1a1b, 1a1c, 1b1c
-individuals that are heterozygous have greater fitness than homozygotes Ex. hybrid
vigor in domestic animals Why?
1)having two different forms of an enzyme gives the individual greater flexibility in
dealing with the environment
2) nonfunctional or harmful alleles are masked by functioning alleles
-sometimes individuals that differ genetically differ in their ability to reproduce. If
individuals with certain alleles are better able to reproduce, then gene frequencies in the
population will change in subsequent generations
-this process where environment causes changes of genes in a group of populations of
the same species (evolution) is called natural selection. When man does the selecting,
it is called artificial selection
14. List and describe two measures of genetic diversity. What is hybrid vigor?
Which measure addresses hybrid vigor?
Community and Ecosystem Diversity
ecosystem = community + environment
Community (biota) = species that occupy an area
Environment (abiota) = physical habitat and interacts with community to form niches
niches= unique set of resources in the environment that each species uses
Ex. plant - soil type, pollination ecology, seed ecology, moisture, sunlight, etc.
-any component of niche may become a limiting resource when it restricts population
Size
15. Discuss each of the terms on this slide in relation to the Colorado River.
2.10 In this illustration, each animal species lives at different depths and in association with certain
structural features
Communities are organized into four trophic levels:
1) Photosynthetic species (primary producers)
-obtain energy via photosynthesis from the sun or some type of chemosynthesis
- mostly plants in terrestrial habitats and algae/cyanobacteria in aquatic habitats
2) Herbivores (primary consumers)
-eat photosynthetic species
3) carnivores (secondary consumers or predators)
-eat herbivores or other carnivores
-omnivores include plants in their diet
4) detrivores (decomposers)
-recycle nutrients through the ecosystem
-mostly fungi and bacteria. Also includes animals like worms, dung beetles,
and vultures
16. Give an example of each level observed on the Colorado River field
trip.
Four trophic levels comprise food chains or webs and the greatest
biomass is usually found as primary producers
-species at the same trophic level that use approximately the same
resources compete with each other = guild
17. Describe a guild observed on the Colorado River field trip.
18. Describe two food chains associated with the river.
19. How are food webs different?
2.13 Field ecosystem showing its trophic levels and simplified energy pathways
2.14 A diagram of a simple food web studied in a traditional agricultural ecosystem.
Species interact within communities in ways beyond trophic levels
Predation and competition as well as limiting resources determine a habitats
carrying capacity = number of individuals at each level that the resources of
the ecosystem can support
Species in the community often interact as symbionts=species found together in
close association and cannot survive without each other
20. Discuss, predation, competition, and carrying capacity in a way that is
associated with the Colorado River ecosystem?
Three types of symbiotic relationships recognized:
1. commensalism (+ 0)
-two species live in close association (symbiosis) where one benefits and the
other is not affected. Ex. epiphytes
2. predator (+ -)
-symbiosis where one species benefits and the other does not
-parasitism is a subclass of predator symbiosis. Ex. Animals are affected by
bacteria, fungi, protozoans, worms, arachnids, and insects. Plants are
affected by bacteria, fungi, protozoa (slime molds), other plants, worms,
and arthropods
3. mutualism + +
-symbiosis where both species benefit. Ex. fruit eating animals, flower
pollinators, lichens
21. Discuss examples of each of the above associated with the Colorado River?
2.12 Mutualistic relationships
(A) Ant and acacia; (B) Hummingbird and legume
Communities change in species composition, community structure, and
physical characteristics in response to natural and human caused
disturbance = succession
Two types of succession
1) Primary
- no soil is present Ex. lava fields, sand dunes
2) Secondary
- soil is present Ex. cleared field reverting back to Cross Timbers ecosystem
22. Discuss examples of each of the above associated with the
Colorado River?
Some species have a greater impact on an ecosystem than others = Keystone species
-because of their impact on the ecosystem, their protection is a priority
-usually have high impact on the ecosystem and low proportional biomas
-can be classed according to the following:
1) major predators
a. sea stars
-one of the best quantified examples and one of first to use the term (Paine, 1966)
-removal of sea stars decreased the richness of mussels, barnacles, snails, and other
species
-one species of mussel dominated and this limited the space for many other species
b. sea otters
-keep shellfish, sea urchin and kelp in balance
Fig. 2.11
c. grey wolves
-keep deer and herbs in balance
Fig. 2.11 When sea stars are present, competition among mollusks is <, & >species occur in habitat
2.13 Keystone species
Box 2.2 Forests of giant kelp provide the starting point and structure for a diverse biological
community
Read box 2.2 and discuss
The sea otter as a
Keystone species.
2) ecosystem engineers
a. beavers
-create wetland ecosystems Fig. 2.16
b. leaf cutter ants
-fungal gardens are habitats for 100s of subterranean species
3) food resources
a. nectar bearing flowers and certain fruits
-comprise less than 1% plant species diversity in the tropical forest yet are essential
parts of food webs
-Ex. Fig wasps pollinate fig flowers that form fruit that is used by dozens of animals
b. flying foxes (bats)
-pollination and seed dispersal for hundreds of tropical plants Fig. Xtra
c. some grazing animals
-species of fish and sea urchins control of weedy algae on coral reefs
Figure 2.16 Beavers are
ecosystem engineers that
build dams across streams,
in the process creating new
wetland habitat. Beavercreated wetlands are
increasing in Minnesota due
to trapping restrictions and
loss of predators
Fig. Xtra Flying foxes are vital pollinators and seed dispersers in Old World tropical forest
communities
4)
decomposers
-dung beetles exist in low densities in tropical forests Fig. 2.15
-bury dung for larvae that releases nutrients
-seeds in dung germinate into a number of fruiting species used by other
animals
-kill parasites in dung keeping vertebrate populations healthy
-losing a keystone species can create a series of linked extinctions called an
extinction cascade
23. Discuss keystone species associated with the Colorado River.
2.17 Dung beetles are important keystone species in many communities
Keystone resources
-certain resources are vital to the functioning of a ecosystem = keystone resources
-these resources occupy only a small portion of the habitat but are crucial to many
species in the community
Examples of keystone resources:
1) salt licks and mineral pools
-greatly affect the abundance of vertebrates
2) deep pools in streams and springs
-refuge in dry seasons
3) flowing water
-essential for some aquatic species
4) hollow tree trunks and rotting wood
-nesting and denning sites for many bird and mammal species
24. Discuss keystone resources associated with the Colorado River.
Key Ecosystem Processes
-influence ecosystem dynamics
Include:
1) transfer of energy through trophic levels
2) production of biomass
3) cycling of nutrients
4) movement of water
5) fire
-key ecosystem processes maintain ecosystem health when stable, resistant, and resilient
25. Discuss key ecosystem processes associated with the Colorado River.
Ecosystem dynamics
Ecosystem integrity-condition where ecosystem is complete in terms
of species composition, structure, and function
Few exist today. Some are stable ecosystems- ecosystems that remain
in the same state
-remain the same as have organisms that are resistant and resilient
Resistance-ability to remain stable even with ongoing disturbance
Resilience-ability to return to stability quickly after disturbance has
occurred
Ex. Non-native fish are introduced to fish-free ponds and the number
of native animal species declines, indicating low resistance but when
the fish die out, the number of native animal species quickly recovers,
indicating high resilience