Can you see the variation in zebras?

        Can you see the Walking Stick insect?

5.4 Evolution

Click4Biology

Review Questions

How We Evolve by Benjamin Phelan   

assignment  vocab  vocab A-Z   background info   assessment

Charles Darwin (1809-1882) published On the Origin of Species in 1859.

5.4.1 Define evolution.

Evolution is the cumulative change in the heritable characteristics of a population.

If we accept not only that species can evolve, but also that new species arise by evolution from pre-existing ones, then the whole of life can be seen as unified by its common origins.

Variation within our species is the result of different selection pressures operating in different parts of the world, yet this variation is not so vast to justify a construct such as race having a biological or scientific basis.

Evolution is the change in traits of a population over generations.

Natural Selection is a theory that explains how evolution happens.

A population is a group of organisms of the same species living in the same area at the same time that  reproduce together.

5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures.

How do we know that evolution happens?

The fossil record, selective breeding, and homologous structures provide evidence of evolution:

• Whale fossils show changes over time.

Michael Shermer, How we Believe: The Search for God in an Age of Science, New York: W. H. Freeman & Company, 2000, pp. 132-133.

• Selective breeding (artificial selection) of dogs shows heritability and change.

• Homologous structures show common ancestry - (similar structures with different functions).

Darwin's Theory of Natural Selection

1. Overproduction of offspring

2. Competition for limited resources

3. Variation in traits among individuals in a population

4. Environmental conditions cause differential survival based on individual traits = selection.

5. Over generations, the traits of a population change due to differential survival = "Descent with modification"

5.4.3 State that populations tend to produce more offspring than the environment can support.

5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival.

5.4.5 State that the members of a species show variation 

Vocabulary:

• adaptation - a heritable trait that helps an organism survive

Overproduction of offspring increases variation and causes competition for resources.

Competition for limited resources causes differences in survival because of variations.

5.4.6 Explain how sexual reproduction promotes variation in a species.

Meiosis creates variation in gametes, and random fertilization creates variation in offspring. 

During meiosis, haploid cells are produced with a variety of allele combinations.

During fertilization, random sprem and random eggs fuse together to produce unique offspring.

5.4.7 Explain how natural selection leads to evolution.

Greater survival and reproductive success of individuals with favourable heritable variations can lead to change in the characteristics of a population.

Variation

• Variation exists in populations due to random mutations and sexual reproduction.

Competition and Overproduction

• Competition for resources occurs within and between species.

Adaptation and Selection

• From the variation in populations, some individuals survive better and reproduce more because of their beneficial traits.
• Beneficial traits that help an organism survive in a particular environment are called adaptations.
• Adaptations are not changes in traits or organsisms to fit with the environment - they are already present in the population. 
• Everything surrounding an organism - predators, prey, diseases, water, temperature, habitat, etc - is the environment which determines which traits are beneficial or not. 

"Descent with Modification"

• Over generations, the population changes as the beneficial traits become more common and the less beneficial traits become less common.

The change in the population over generations is evolution.

Because of variations and ongoing changes in environments, which traits are good or bad can also change.

5.4.8 Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria.

Other examples could include: the changes in size and shape of the beaks of Galapagos finches; pesticide resistance, industrial melanism or heavy-metal tolerance in plants.

Example of evolution of bacteria due to antibiotics

Staphylococcus bacteria overproduce and show variation.

The variation includes a trait for resistance to the antibiotic "methicillin." 

Some bacteria are not affected by the antibiotic. Other bacteria are killed by it.

The use of the antibiotic is a selective agent in the the bacteria's environment.

The bacteria with the resistant trait have an adaptation. They are selected for.

The bacteria without the resistant trait are selected against - they die.

The population of bacteria changes as the number of bacteria with the resistant trait increases over time.

Darwin's Finches

The population of finches on mainland Ecuador had natural variation in traits.

The population colonized various islands of the Galapagos.

Each island had a different primary food source. This was a selective agent in the environment.

The finches with traits that helped them acquire food survived and reproduced more than finches with different traits.

Over generations, the population on each island changed as the adaptation became more common.

Over time, each island evolved a separate species of finch.

5.5 Classification

Living things are organized into groups based on similarities and differences. The highest level of grouping is the domain. There are three domains. The Eukarya domain includes all eukaryotic organisms (plants, animals, fungi, and protists). Prokaryotic organisms are divided into two domains: Archaea and Bacteria. The Archaea domain includes bacteria that live in extreme environments (very hot or salty, very high or low pH). The Bacteria domain includes bacteria that have distinct DNA and membranes from the Archaea; they are normally considered the common bacteria of most environments.

5.5.1 Outline the binomial system of nomenclature.

TOK: The adoption of a system of binomial nomenclature is largely due to Swedish botanist and physician Carolus Linnaeus (1707–1778). Linnaeus also defined four groups of humans, and the divisions were based on both physical and social traits. By 21st-century standards, his descriptions can be regarded as racist. How does the social context of scientific work affect the methods and findings of research? Is it necessary to consider the social context when evaluating ethical aspects of knowledge claims?

Binomial Nomenclature

Binomial = two names

Nomenclature = naming system

The scientific name of a species has two names. The first name is the genus; the second identifies a particular species of the genus.

Both names are always written together. One name does not identify the species.

Example: modern human = Homo sapiens

"Homo" is the genus name. It also includes our extinct relatives, like, Homo habilis and Homo erectus.

Notice the genus is always capitalized and the scientific name is also in italics or underlined.

5.5.2 List seven levels in the hierarchy of taxa—kingdom, phylum, class, order, family, genus and species—using an example from two different kingdoms for each level.

Taxonomy: the study of classification - ordering and arranging in groups based on similarites and differences. 

Taxa: one level of a hierarchy of groups (groups within groups)

Taxa are ranked from largest group to smallest group, also from most general to most similar:

Kingdom - largest group

Phylum - (called Division for plants)

Class

Order

Family

Genus

Species - smallest group, one kind of organism

Mneumonic device: "King Phillip couldn't order five good sandwiches."

Example: modern humans - Homo sapiens

Kingdom: Animalia (Anmals)

Phylum: Chordata (Vertebrates- backbones)

Class: Mammalia (Mammals)

Order: Primates

Family: Hominidae (Human-like)

Genus: Homo (modern and ancestor humans)

Species: Homo sapiens (modern human)

Example: rice - Oryza sativa

Kingdom: Plantae (plants)

Division: Magnoliophyta (flowering plants)

Class: Liliopsida (monocots - one seed leaf)

Order: Cyperales

Family: Poaceae (grass group)

Genus: Oryza (rice group)

Species: Oryza sativa (human cultivated species)

5.5.3 Distinguish between the following phyla of plants, using simple external recognition features: bryophyta, filicinophyta, coniferophyta and angiospermophyta.

Kingdom: Plantae

Plants are divided into four main groups (called "divisions" instead of "phyla") based on their external structures.

Divisions (Phyla):  1) bryophyta, 2) filicinophyta, 3) coniferophyta, and 4) angiospermophyta

Bryophyta

                                  http://tommyimages.com                                                 http://www.saburchill.com/ans02/chapters/chap041.html

Bryophyta - mosses

• no vascular tissue (water or food transport tissue): no leaves, stems, or roots 
• reproduce by spores
• live near water or in very moist environments
• short

Filicinophyta  

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Filicinophyta - ferns

• vascular tissue: roots, stems, and leaves
• reproduce by spores
• distinctive fronds (leaves)
• taller

Coniferophyta  

Coniferophyta - pine trees and conifers

• vascular tissue
• reproduce by seeds, but without fruit, usually on "cone" structures
• distinctive narrow needle-like leaves
• shrubs and trees: woody stems

Angiospermophyta  

Angiospermophyta - flowering plants

• vascular tissue
• reproduce by seeds within fruits from flowers
• variety of leaves
• variety of sizes: trees and shrubs with woody stems; herbaceous (soft, green) stems

5.5.4 Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda.

Kingdom: Animalia (contains more than 30 phyla, but we'll only study 6)

Phyla: Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, and Arthropoda

External characteristics include: body layers, mouth to anus system, support system, and body plan (symmetry).

Body plans: asymmetrical, bilateral symmetry (two mirrored halves), and radial symmetry (multiple mirrored halves from one point).

Asymmetrical is a random shape like a sponge. Bilateral is like a human - two halves. Radial is like a wheel or starfish - many halves around one point.

Porifera - sponges are the simplest form of multicelluar animals.

Porifera. © 2004 Dlloyd http://tolweb.org/treehouses/?treehouse_id=3431   http://www.cartage.org.lb/en/themes/sciences/zoology/animalmorphology/listanimalphyla/listanimalphyla.htm

• Body layers: no layers or tissues, but does have groups of specialized cells
• Mouth/Anus: none
• Support: "Spicules," hard fibers that give support
• Asymmetrical body plan
• Body plan includes "canals" for water to flow through for filter feeding

Cnidaria - jellyfish, anemones, corals, hydras are known for their stinging cells

• Body layers: two layers
• Mouth/Anus: one openning for entrance and exit of nutrients and waste
• Support: jellies, anemonies, and hydras have only soft tissues ; some corals produce hard mineral "skeletons"
• Body plan: radial symmetry 
• Some can move ; some are sessile 

Platyhelminthes - flatworms are unsegmented worms, some are parasites

• Body layers: three layers
• Mouth/Anus: one openning for entrance and exit of nutrients and waste, but it has complex folds
• Support: only soft tissues
• Body plan: bilateral symmetry 

Annelida - segmented worms

• Body layers: three layers
• Mouth/Anus: two opennings (mouth and anus) for entrance and exit of nutrients and waste
• Support: only soft tissues
• Body plan: bilateral symmetry 
• The body is divided into segments that have specialized functions
• Internal organ systems (nervous, circulatory, digestive, etc) 

Mollusca - snails, bivalves, squids, and octopi vary greatly but are known for three distinct body sections 

• Body layers: three layers
• Mouth/Anus: two opennings (mouth and anus) for entrance and exit of nutrients and waste
• Support: various: only soft tissues for slugs, shells for bivavles, protein "skeleton" in squid
• Body plan: bilateral symmetry 
• The body is divided into three segments that have specialized functions: muscular "foot" for movement; "body" for organs; and "mantle" a special covering that secretes shells or is adapted for other specialized functions
• Internal organ systems (nervous, circulatory, digestive, etc)

Arthropoda - insects, crustaceans, arachnids (spiders), centipedes, millipedes.

• Body layers: three
• Mouth/Anus: two opennings - digestive tract
• Support: exoskeleton - a hard external skeleton made of the protein chitin.
• Body plan: bilateral symmetry
• The body is divided into segments with jointed appendages.
• Internal organ systems (nervous, digestice, circulatory, etc)

5.5.5 Apply and design a key for a group of up to eight organisms.

A dichotomous key should be used.

A dichotomous key is tool for identifying an unknown species.

It is a series of questions about characteristics, each with with only two answers.

The answers lead to new questions, until the species can be identified.

Elliott's Dichotomous Key

Example Dichotomous Key

Another Example Dichotomous Key

Design a key for eight organisms from the animal classification above.

Design a key for the organisms below.