evolution & biodiversity: origins, niches and adaptation © brooks/cole publishing company / itp

Evolution & Biodiversity: Evolution & Biodiversity: Origins, Niches and Origins, Niches and

AdaptationAdaptation

© Brooks/Cole Publishing Company / ITP

1. Life on Earth1. Life on Earth


Two main types of life:

• Prokaryotes- (means "before nucleus") organisms (bacteria) whose cells do not have a distinct nucleus or other internal parts enclosed in membranes.

• Eukaryotes- (means "true nucleus") organisms whose cells have a distinct nucleus and various internal parts enclosed in membranes.

Biodiversity- (=biological diversity) variety of different species, genes, or ecosystems.

Six KingdomsSix Kingdoms


Living organisms are classified into six kingdoms:

•Eubacteria•Archaebacteria•Protista (protists)•Fungi•Plantae (plants)•Animalia (animals)



• Eubacteria and archaebacteria- single–celled, microscopic prokaryotic organisms, in particular bacteria and cyanobacteria.

• Protista (protists)- mostly single–celled eukaryotic organisms, such as diatoms, dinoflagellates, amoebas, golden–brown & yellow–green algae and protozoans.



• Fungi- mostly many–celled (some single–celled) eukaryotic organisms, such as mushrooms, molds, mildews and yeasts.

• Plantae (plants)- mostly many–celled eukaryotic organisms, such as red, brown and green algae, mosses, ferns, conifers and flowering plants.



• Animalia (animals)- many–celled eukaryotic organisms, including invertebrates (e.g., sponges, jellyfish, sponges, mollusks, worms, arthropods) and vertebrates (e.g., fish, amphibians, reptiles, birds and mammals).

What is a Species?What is a Species?


Species- a distinct kind of organism; groups of organisms that resemble each other and, in cases of sexually reproducing organisms, can potentially interbreed.

• Each known species is assigned a scientific name (derived from Latin) consisting of two parts (genus + species) which is always written in italics or underlined.

examples: Ursus horribilis is the grizzly bearTaraxacum officinale is the dandelion

• Each species is classified in a hierarchical taxonomic classification:

kingdom, phylum, class, order, family, genus, species


Classification of OrganismsClassification of Organisms

Example of the classification of human beings.


Classification of OrganismsClassification of Organisms

Example of the classification of human beings (continued).

All Living Things Have Genetic MaterialAll Living Things Have Genetic Material

The universal genetic code, A, G, C, and T tie all living things together and show their relatedness.

Every population of a species has a gene pool

Members of a population generally have the same number and kinds of genes.

A particular gene may have two or more different molecular forms, called alleles– I.e. eye color B for brown and

b for blue

2. Origins of Life2. Origins of Life


Summary of the evolution of the earth and its life over the past 4.7 to 4.8 billion years.

Why is Earth "just right" for life?Why is Earth "just right" for life?


• Distance from sun: leads to a temperature favorable to life (for liquid water); energy flow from sun sufficient to drive weather and supply energy for life

• Size: enough gravitational mass to hold atmosphere of light molecules (N2, O2, CO2, and H2O) and to keep core molten

• Rotation: leads to daily patterns (night & day)

• Orbit around sun: leads to seasonal patterns

• Atmospheric evolution: accumulation of O2 in lower

atmosphere; formation of ozone shield to screen harmful ultraviolet (UV) radiation.

What Evolution Is Not:What Evolution Is Not: It is NOT a fact…..it is a theory: a highly

probable explanation affecting all biological phenomena, with much supporting evidence, and NO evidence against it

It is NOT something one should believe in….it is based on science NOT faith

It is NOT just concerned with the origin of humans….no more or no less than any other species.

It was NOT first explained by Darwin….many people proposed the idea long before Darwin

It is NOT something which happened only in the past….it is still going on.

What Evolution Is Not:What Evolution Is Not: It is NOT something that happens to individuals…ONLY

populations It is NOT accidental or random (mutations are)…it is

influenced by environment and other factors It was NOT developed to undermine religion…it was

developed to explain observations of life in a testable way. It does NOT deny the existence of God….it is neutral; God is

neither required nor eliminated.

What Evolution Is:What Evolution Is: Idea that populations of species

change over time. New species develop from earlier

species by accumulated genetic mutations—descent with modification– Life comes from life– Speciation proceeds with time,

increasing numbers of species that become increasingly different.

– All species we see today are the growing tips of a branching tree: close clusters of tips have most recently branched (evolved)

Found to be supported in all cases Holds the high status of near

certainty…it is Scientific Theory

3. Evolution & Adaptation3. Evolution & Adaptation


Evolution- the change in a population's genetic makeup through successive generations.

• Microevolution- change in gene frequency within a population (short–term evolutionary changes) due to beneficial changes (mutations) in DNA being passed on to offspring

• Macroevolution- formation of new species from ancestral species (long–term evolutionary changes).Other species are lost through extinction.

Genes mutateindividuals selectedpopulations evolve

MicroevolutionMicroevolution


Four processes drive microevolution:

1. Genetic variability: Random mutations serve as the ultimate source of genetic variation that results in changes in a population’s gene pool over time.

-Exposure of DNA to external agent-Random mistakes in DNA replication-Only mutations that occur in

reproductive cells can be passed on to future generations

2. Natural selection: the process by which some individuals of a population have genetically based characteristics that cause them to survive and produce more offspring than other individuals.

MicroevolutionMicroevolution

3. Gene flow: the movement of genes between populations;

4. Genetic drift: change in genetic composition that results by chance, especially in small populations

Four processes drive microevolution, cont:

Natural SelectionNatural SelectionThree conditions required for natural selection:

• Variability: there must be natural variability for a trait within a population

• Heritability: the trait must be heritable, such that it can be passedfrom generation to generation

• Differential reproduction: the trait must enable individuals with the trait to leave more offspring than other members of the population.

Adaptation- a heritable trait that enables organisms to better survive and reproduce within a given set of environmental conditions.

Will they surviveand reproduce?

Natural SelectionNatural Selection


Example: peppered moth (Biston betularia)

• Variability: two color forms, one dark and one light; light form originally more common because it blended in with lichens on

• Heritability: color form was genetically based

• Differential reproduction: In industrial revolution mid–1800s in England soot coated trees dark form became more common because they survive to reproduce

Classic example of microevolution – change in gene frequency in a population.



Directional selection favors individuals with traits that are at one end of a distribution (such as the peppered moth example).

"It pays to be different.”Video-click through



Stabilizing selection eliminates individuals at both ends in the spectrum of variation; the average remains the same.

"It pays to be average.“

Video--click through



Disruptive (diversifying) selection eliminates average individuals, but favors individuals at either extreme of the spectrum of variation.

"It doesn't pay to be normal.“

Video--click through

CoevolutionCoevolution


Coevolution- interactions between two species that result in ongoing evolutionary changes in each of the species. Changes in the gene pool of one species can lead to changes in the gene pool of the other.

**Competitive relationships lead to coevolution.

Examples:

• Moths with sensitivity to sound frequencies of bats will be selected for. Bats then with different frequencies moths can’t hear will be selected for, etc.Bats vs. Moths--7min

• Plants with defenses against herbivores (thorns, camouflage, toxins) and their herbivores (ability to deal with defenses).

• Camouflage

Ecological Niche vs. HabitatEcological Niche vs. Habitat


Niche- the functional role of a species in an ecosystem—it’s occupation.Includes:

• Range of tolerance for conditions (physical and chemical)

• Resources the species uses (nutrients or food)

• Interactions with living (biotic) and nonliving (abiotic) components of ecosystem;

• Role in flow of energy cycling of matter.

Habitat- the actual location where an organism lives—it’s address.

Ecological NicheEcological Niche Fundamental niche- full potential range of physical,

chemical and biological conditions and resources a species could theoretically use if there were no competition

Realized niche- actual niche a species occupies that represents only part of its fundamental niche. This partial occupation of its fundamental niche is due to competition

Generalist vs. Specialist SpeciesGeneralist vs. Specialist Species Scientists use the niches of species to

broadly classify them as generalists or specialists– Generalists- broad niches, eat a wide

variety of food, tolerate a wide range of environmental conditions, more secure under rapidly changing conditions,

Cockroaches, mice, white-tailed deer, humans etc.

– Specialists- narrow niches, able to live in only one type of habitat, tolerate only a narrow range of environmental conditions, more secure when conditions constant b/c fewer competitors due to their specialization

Tiger salamanders can only breed in fishless ponds

Region of niche overlap

Generalist specieswith a broad nicheSpecialist species

with a narrow nicheNiche

breadth

Nicheseparation

Nu

mb

er

of in

div

idu

als

Resource use

Ecological Niche and ConvergenceEcological Niche and Convergence


Relation between ecological niche and convergence:

• Species with similar niches tend to evolve similar sets of traits

• Convergence- the resemblance of different species with similar niches

• Examples of convergence:

- Desert shrubs of different parts of world have deep roots, small leaves, and high tolerance to hot, dry conditions.

- Herbivores of different parts of world have traits to forage and digest plant material, escape predators, and migrate or become dormant when food is scarce.

4. Speciation, Extinction, & 4. Speciation, Extinction, & Biodiversity Biodiversity


Macroevolution-changes in evolutionary lineage over much longer periods.

Involves three processes:

• Evolutionary change of lineage through time

• Speciation- formation of new species

• Extinction- loss of species

New species typically evolve by two steps:

• Geographic isolation – separation intodistinct populations with different evolutionary pressures

• Reproductive isolation – evolutionary changes in each population that prevent interbreeding when populations come into contact.

SpeciationSpeciation


Geographic isolation can lead to reproductive isolation, divergence and speciation.

ExtinctionExtinctionFossil record shows evidence of extinction as a natural process:

Biologists estimate that 99.9% of all the species that ever existed are now extinct.

• Background extinction- loss of species at a relatively low rate, often due to changes in local conditions

• Mass extinction- abrupt increases in extinction rates above the background level

• Believed to result from global climate changes

• Recent extinctions caused by humans at exceptionally high rates.

Continental DriftContinental Drift


Continental drift, the slow movement of continents, has played a major role in both speciation and extinction.

EURASIA

AFRICASO

UTH

AM

ER

ICA

IND

IA

135 million years ago

Present65 million years ago

225 million years ago

120°80° 0°

120°120°

120°

80°80° 80°80°40°

40°120° 120°

120°GONDWANALANDGONDWANALAND

120°

LAURASIALAURASIA

PA

NG

AE

A

PA

NG

AE

A

ANTARCTICAANTARCTICA AUSTRALIA

AUSTRALIAMADA-

GASCARMADA-

GASCAR

Adaptive RadiationAdaptive Radiation


Adaptive radiation- involves splitting of a lineage to form many species with different ecological niches The adaptive radiation of mammals began about 65 million years ago.

Adaptive RadiationAdaptive Radiation Earth’s mass extinctions and depletions have been followed by

periods of recovery -adaptive radiation Numerous new species evolved to fill new or vacated niches. Speciation – extinction = biodiversity The existence of millions of species today means that

speciation on average has kept ahead of extinction for the past 250 million years, but this increase has leveled off.

5. Sustainability & Evolution5. Sustainability & Evolution


What is the appropriate time frame for thinking about environmental problems?

• Humans have barely existed in geological or evolutionary time scales

• Earth's biodiversity has taken millions of years to evolve

• Extinction is natural process, but human–induced extinction is occurring at unprecedented rates 100-1,000 X’s the natural background extinction rate

• EXTINCTION IS FOREVER!

The Future of Evolution: Genetic The Future of Evolution: Genetic EngineeringEngineering

Artificial selection- has been used to by farmers for millennia to change genetic characteristics of populations by selecting one or more desirable genetic traits and selectively breeding them.

Genetic engineering- used to create genetically modified organisms (GMO’s) by transplanting genes from one species to the DNA of another.– Has great promise– Unpredictable—trial and error– Future problems with results

can’t always be anticipated

GMO’s and GMF’sGMO’s and GMF’s Advantages:

– Increased nutritional value– Greater crop yield– Medicinal benefits such as addition of

vaccines or removal of allergens from food

– Resistance of plants to pests so decreased use of pesticides

– Resistance of plants to herbicides so weed tilling can be decreased resulting in less soil erosion

GMO’s and GMF’sGMO’s and GMF’s Disadvantages:

– Possible production of new allergens or toxins by GMF’s due to mutation

– Decrease in genetic diversity by planting only a few “superfoods.”

– Cost of raising/growing food will increase due to high costs of creating and patenting GMF’s. Drive out some independent farmers

– Pest populations may become resistant to some pesticides.

– Grocery Store Wars

Organic CertificationOrganic Certification Fruits, veggies, livestock and eggs can

all be certified organic. How?

– Avoidance of most synthetic chemicals:

AntibioticsPesticidesFertilizerFood additives

– No GMO’s or irradiation– No use of sewage sludge for

fertilization– Use of farmland that has been free

from chemicals for a # of years

evolution & biodiversity: origins, niches and adaptation © brooks/cole publishing company / itp

Documents

reproducing organisms

nucleus organisms bacteria

true nucleus organisms

dandelioneach species

parts genus species

known species

distinct nucleus

classification of human