SBI 4UO LESSON PLANS

Ontario Curriculum objectives: U=understanding concepts (U1-U4) D=developing skills (D1-D5) R=relating science (R1-R2)

Text: Biology 12, Nelson

Evolution the process in which changes to genetic traits of a species occur over time

As evidence for evolution of species was accumulated, theories to explain these facts were proposed

This unit will discuss scientific theories to explain the evolution of species

The following terms must first be discussed:

Species
Common definition of species:
-a reproductively isolated group of organisms
-one species can produce fertile offspring only with others of the same species
-populations of one species  may be reproductively isolated by geographic barriers but still capable of interbreeding when reintroduced

However, this definition of species is flawed.
-the following exceptions occur to common definition of species:
(a) some organisms never produce sexually
     e.g. amoebas only reproduce by mitosis
(b) some organisms produce only some fertile offspring
     e.g. the fruit flies D. melanogaster and D. simulans produce fertile females but sterile males
(c) some organisms have two sexes, but only females are involved in reproduction which is asexual
     e.g. 20 lizard. 2 salamander and 4 fish species
(d) some organisms overlap in two areas of the world, but are only able to interbreed in one of those areas

When the common definition of species breaks down, phenotype (appearance) and niche (role in environment) are used to classify species
When discussing evolution of a species it is important to remember what definition of species you are using, as there is no unified species concept in biology because of the wide variety of reproductive systems found in nature

This unit will discuss scientific theories to explain the evolution of species

Scientific Theories
A theory is an explaination of observations/evidence.
In order to be considered scientific, a theory:
(a) is guided by natural laws. (e.g. law of gravity, electrostatic charges, inertia)
(b) has to be explanatory by reference to natural law. Supernatural explanations are not proposed in scientific theories.
(c) is testable against the empirical world. Some experiment could potentially be devised to test the theory.
(d) has tentative conclusions. Scientific answers are not the final word, not ABSOLUTE.
The fact that scientific answers are not absolute does not imply they are not valid  
(e) is falsifiable. Some evidence could potentially be found to prove a theory false.
If this evidence is not found the theory remains valid, but if this evidence could not even be postulated, the theory is not scientific

1650: James Ussher p. 510
Significance: early estimate of age of earth, very short with little time for evolutionary change
-estimated the age of the earth as being created in 4004 B.C. using information from written sources
-the ages of various people mentioned in the bible at the times of the birth of their offspring were used
-archeological evidence showed the oldest human civilizations known in Egypt were a few thousand years old
-the bones of ancient Egyptian inhabitants were the same as present human bones
-organisms were thought not to have changed since the origin of the earth (immutable)
-Usshers estimate of 4004 B.C. was published in the King James bible in 1701, after his death

1740: Georges Buffon
Significance: estimated earth's age as much older than originally thought, proposed similar organisms were related
-wrote the 36 volume “Histoire Naturelle” summarizing present scientific knowledge
-suggested a series of gradual changes mixed with catastrophic changes occurred in the earth history
-suggested the earth was formed by a catastrophic collision of the sun with a massive body of matter
-thought it would last 90 000 years before cooling completely from this collision
-estimated the age of the earth through this cooling as 72 000 years, well above previous estimates
-believed fossil indicated past life but denied the possibility of extinction
-postulated common ancestors to similar organisms

1809: Jean Baptiste Lamarck
Significance: proposed first straight forward theory to explain evolution of species, Marche de la Nature
Theory: Marche de la Nature
-proposed that organisms moved up Aristotles scale of nature (Scala Naturae)
-one celled organisms progress towards more complicated multicellular organisms
-as species ascend this scale, organisms lower on scale also ascend
-new organisms are spontaneously created to prevent gaps from forming in the scale
-there is no extinction, only progression
-progressive changes are the result of use or disuse of a part during the organism's life
-these altered traits are inherited by offspring

Why is this not a scientific theory?
-supernatural force creates new organisms and helps provide direction of evolutionary change, along with the environment
-supernatural forces are not explanatory with reference to natural laws

1813: Georges Cuvier p. 513
Significance: founder of paleontology, proposed theory to explain evolution of species, Catastrophism
-studied fossils and realized species could become extinct
-noticed discontinuities in fossil record and different fossils were found in different layers of rock
(aside: he is buried in the same Paris cemetery as Jim Morrison...like you care...but his brain is elsewhere...apparently it was really big, so became quite the conversation piece in the 1800's...woo hoo)
Theory: Catastrophisms
-all organisms present on earth are killed by a catastrophe (e.g. flood)
-new organisms were formed which replaced and improved on previous organisms
-progressivism occurs (successively better creations)

Why is this not a scientific theory?
-supernatural force causes the catastrophe, creates new organisms and provides direction of evolutionary change
-supernatural forces are not explanatory with reference to natural laws

1830: Charles Lyell p. 517
Significance: founder of modern geology, proposed scientific theory to explain geological change
James Hutton had watched the slow erosion of hills by streams and postulated that geological processes worked very slowly
Charles Lyell took this idea and expanded to establish geology as an empirical science
Theory: Uniformatarianism
-geological changes in the past can be explained using natural geological processes that are working in the present (e.g. erosion)

This is a scientific theory.

1798: Thomas Malthus
Significance: founder of modern economics, proposed populations will struggle for limited resources
-Malthus was an English clergyman and professor of economics (England's first)
-wrote "An Essay on the  Principle of Population"
-proposed populations increase geometrically, but food production increased arithmetically
-when food ran out a struggle for existence would ensue
-Malthus was arguing that aid to the poor was counterproductive (nice guy)
-while neither Darwin nor Wallace had no sympathy for the social views of Malthus, they did find inspiration in the idea of a struggle for limited resources

1858: Alfred Russel Wallace
Significance: independently formulated scientific theory to explain biological change by natural selection                            
-naturalist working in South America, collecting specimens
-during a bout of yellow fever it occurred to him to apply Malthus' struggle for survival to nature
-independently formulated the theory of natural selection as a mechanism for evolution.
-wrote to Charles Darwin, presenting his theory in a paper (Darwin was naturally shocked and stunned)
-Charles Lyell arranged the joint reading of papers by both Darwin and  Wallace on the same evening (July 1, 1858)
-neither author was present at the reading although it was conducted to the satisfaction of both men

Darwin wrote a book to explain natural selection called "On the Origin of Species by Means of Natural Selection"
This book was published in 1859 and became a best seller

Natural Selection was considered a radical evolutionary theory because it proposed a natural force controlling the direction of biological change...

Comparison of Marche de la Nature and Natural Selection
Both the Marche de la Nature and Natural Selection share the following feature:
-change in the environment resulted in evolutionary change within organisms
The two theories differed in the following point concerning the effect of the environment:
-Natural Selection proposed selected variations were already present in the population
-those variations that survived were the ones best able to exploit the environmental change
-Marche de la Nature proposed selected variations arose during the lifetime of the organism
-those variations were caused by responses to environmental change

Microevolution:
-evolution of new traits within a species
e.g. evolution of insecticide resistance in fruit flies, antibiotic resistance in bacteria

Microevolution explained by Marche de la Nature and Natural Selection:

Aspects of Natural Selection
-Darwin and Wallace could only speculate on how selected variations originated in a population
-we now know that variations arise by mutations
-sexually reproducing organisms get additional variations by crossing over, independent assortment and fertilization

What provides the direction of evolution?(natural selection is not a random process)
-the environment provides the direction by selecting which variations are more favourable and which variations are less favourable
-as long as offspring show additional variations, environmental selection will result in a continual change in the population

 
Macroevolution:
-evolution of new species
-microevolution occurs to such an extent that two previously interbreeding populations are no longer able to interbreed
-SPECIATION (formation of new species) occurs 

MACROEVOLUTION as explained by natural selection:

*note: evolution occurs in populations, not individuals

Factors involved in macroevolution:
Stability Factors:
-factors which keep the population similar from generation to generation
-e.g. interbreeding lack of new environmental pressure, mitosis
Change Factors:
-factors which result in organisms changes from one generation to the next
-e.g. mutations, crossovers, independent assortment, fertilization
Guiding Factors:
-factors which select the trait that is most successful from the variations present
-e.g. the environment

How could woolly mammoths have evolved from elephants?

Knowledge of genetics and other evidence has shown natural selection to be the major mechanism for the selection of traits in nature (we will do an evidence lab in a few periods)

-view video on evolution

Work on fossil lab

The fossil record provided evidence that evolution of living organisms had changed and led to the development of the first theories to explain this evolution
Fossils are found in layers, or strata, and often show progressive changes between strata
e.g. starfish have been found in three different strata. In the upper (more recent) strata starfish are thicker and more complex than those found in the lower strata

Long periods without fossil change followed by rapid change with strata indicates the punctuated equilibrium has occurred

Fossils examined in this lab are a mix of gastropods, trilobites (extinct), crinoids, arthropods from a variety of eras (Paleozoic (250-600 million years ago), Mesozoic (80-250 million years ago) and Cenozoic (present to 80 million years ago).
Be sure to examine the dinosaur bone, feces fossil and fern fossils.

Examine skulls of the following from the Royal Ontario Museum (now ours)

Pan troglodytes (modern chimpanzee)
-sexual dimorphism exists: male chimps have large incisors, females do not (this is involved in competition for mates)
-post orbital constrictions, smaller brain case, larger face and jaw
-450 cc brain case
-foramen magnum is located further towards back of skull, less upright walking
-upper dental arch is rectangular (chimp feature)

Australopithecus africanus
-lived 3 million years ago/South Africa
-bipedal, erect posture
-440 cc brain case, steep forehead, large face
-large incisors in both sexes

Australopithecus boisei
-lived 2.2-1.2 million years ago/East Africa
-520 cc brain case
-sagittal crest indicates muscle attachment at top of head for chewing
-small incisors, large molars/premolars for grinding food

Homo erectus
-lived 2 million years ago/migrated out of Africa
-1000 cc brain case
-human-like body proportions
-smaller molars than Austalopithecus boisei

Homo sapiens neaderthalensis
-lived 135 000-30 000 years ago/Europe and Middle East
-1500-1800 cc brain case (larger than ours)
-some culture (lived in caves, cared for elderly)

Homo sapiens sapiens
-100 000 years ago to present
-us
-1200-1400 cc brain case
-larger brain case:face ratio than all others listed
-upper dental arch is rounder (human feature)

Fossil Record:
-when fossils are arranged in order of the age of rock (strata) they are found in, progressive changes are seen
e.g. Starfish have been found in three different strata
-in the upper stratum, starfish are thicker and more complex than those found in lower stratum

Homologous Structures:
-organs exist which show similar structure, although the function of the organ may differ from organism to organism
-this suggests a common ancestry to explain the common structure
e.g. vertebrates contain the same general pattern of bones, muscles, nerves blood circulation
-same structure of 5 fingers, 14 bones found in land mammals hand (e.g. gorilla) and water mammals flipper (e.g. whale), but function is different

Analogous Structures/Parallel Adaptation:
-organs exist which show similar function, although the structure of the organ is different from organism to organism
-this suggests evolution to fill similar niches has occurred in different areas, using similar selection pressure and different inherited variations
e.g. most land animals native to Australia fill similar niches to placental animals found elsewhere, yet most are marsupial
-the niches in both locations are similar (e.g. placental anteater and marsupial nubat both eat ants but are not closely related)

Vestigial Structures:
-organs with no apparent function or reduced function exist, but similar organs are functional in other organisms
-this suggests these organs had a function in ancestors, but this function has ceased
e.g. mammalian baleen whales have pelvic bones (hip), even though this bone serves no function, while land mammals support legs with pelvic bones

Patterns of Distribution:
-inhabitants of ocean islands resemble forms of the nearest mainland, but show some differences
-this suggests these forms migrated to the islands and then evolved from a common group
e.g. similar finches are found in the Galapagos Islands and the South American mainland nearby, although the beaks and niches of these finches are quite different

Artificial Selection:
-domesticated species have been selected for certain traits by humans
-this indicates that selection does result in evolution of traits, and perhaps the environment can select traits as well (not just us)
e.g. many breeds of cattle and sheep exist through the selection by farmers in different parts of the world for different advantageous traits

Development:
-during development organisms thought to be related show some similarities in their developmental stages
e.g. vertebrate chickens, human and rabbits all contain gill slits and tails at an early stage of embryonic differences

Molecular Record:
-organisms thought to be closely related show greater similarity in their genes, while those less related show greater differences
-this implies a more recent ancestor between the more genetically similar organisms
e.g. horses and cows have very similar DNA in their genes for hemoglobin, while chicken DNA is very different for this gene
-this implies horses and cows are more closely related to each other than to chickens...no kidding

Work on Evidence for Evolution Lab:
Theories:
-questions examine catastrophism, scala naturae and natural selection
Homology:
-comparison of mammal limb bones
Analogy:
-comparison of different approaches to flight (bat, locust), differences in placental and marsupial organisms, differences in human and panda opposable thumbs
Vestigial Structures:
-discuss reduced function of human appendix (some autoimmune function, not vital for digestion)
Embryology:
-compare embryo of hog, human and rabbit
More Theories:
-distinguish  between gradualism and punctuated equilibrium
Molecular Record:
-create a cladogram for three types of fruit flies, comparing proteins
Fossil Record:
-examine a fossil and compare to present organisms
Further Questions:
-describe thermodynamics, explaining why it does not "disprove" evolution, suggest origin of mitochondria and chloroplasts

Examine Questions in evolution:
What are Hallucigenia? Why has the appearance changed?
-this was a soft bodied organism (few fossils) and with the discovery of new fossils the structure is revised.(less freaky looking now)

Why does the Kiwi lay such big eggs?
-evidence indicates that the Kiwi has evolved from a large size to a smaller size, but  the eggs have stayed large (large Moa bones have been found)
-the explanation hinges on what evidence has been found
New evidence = New explanation

Midwife toads forced to mate underwater develop nuptial pads over a number or generations
-while this seems to imply the Marche de la Nature theory, it is more likely artificial selection of a repressed gene already present in these toads

Finish evidence for evolution lab.

Mimicry is the deceptive resemblance of one species to another species

Batesian mimicry:
-palatable organisms mimic poor tasting organisms
-poor tasting orange monarch butterfly and palatable orange viceroy have been used as examples of this, but on a walk with me kiddies through the Royal Botanical Gardens I saw a presentation saying that viceroy have been found to be poor tasting as well. Not having chowed down on either, I am going to have to discard this example. Who am I to argue with the queen?

Mullerian mimicry: T
-two poor tasting organisms mimic each other (O.K., the monarch and viceroy)

Self-mimicry:
-organisms may have an inconspicuous head and a bold conspicuous tail that mimics a head (you may know people like this)
-when predators attack the "head" only the tail is lost and the organism may survive the attack

Aggressive mimicry:
-a predator may mimic a harmless organism in order to be more successful
-e.g. ant lions use wax cover similar to that found on aphids in order to "fool" the ants, which they eat

Reproductive mimicry:
-organisms mimic others in order to aid in reproduction
-e.g. some flowers resemble insects in order to att