Tag Archives: evolution

The Science of Human Evolution

human_evolution

Video Source (YouTube, 54.42 min)

  1. What vestigial organ, a remnant from our primate ancestors, is apparent in humans?
  2. Which species does the video refer to as our “distant cousins”?
  3. Name three characteristics that we share with these monkeys.
  4. Notharctus tenebrosus is a fossil that scientists believe to be a common ancestor of humans – how old is this fossil?
  5. What feature of this fossil’s hand is important for climbing and gripping objects?
  6. How was colour vision an important evolutionary advantage in early primates?
  7. What genetic mutation occurred to allow primates to see in colour like humans?
  8. What sense diminished as humans evolved high-colour vision? What evidence is there for this?
  9. ‘Lucy’ is a 3.2 million year old fossil from Ethiopia – why is this fossil significant?
  10. What advantages does this particular characteristic give the species?
  11. What disadvantages does bipedalism have for modern humans?
  12. What characteristic of stone-age man is an indication that human ancestors had the ability for complex thought, together with highly developed hand-eye co-ordination?
  13. In what test do 3 month old monkeys out-perform human babies?
  14. What fundamental brain architecture do all vertebrates, including sharks and humans, share?

Unit 4: Area of Study 2: Change over time

Sperm_whale_drawing_with_skeleton

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“The theory of evolution by natural selection, first formulated in Charles Darwin’s book “On the Origin of Species” in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits.”

“Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as be the main process that brings about evolution.”

What is the evidence for evolution? from Stated Clearly (YouTube, 11.21min)

  • Fossil evidence – organisms have changed over time and some have become extinct
  • Comparative morphology (anatomy) – there are similarities between some organisms that suggest a common ancestor
  • DNA evidence – Similar species have more genes in common than dissimilar species, suggesting a common ancestor; Chimpanzees and humans have 99% of their DNA in common
  • Distribution of species (biogeography) shows that islands have unique species, due to an original inhabitant becoming adapted to its’ environment over many generations, by natural selection
  • Similarities of embryos suggest that all vertebrates have a common ancestry

Tree of Life video HD with David Attenborough (YouTube, 6.29 min) – Complete the student worksheet – Highlighting important stages in evolution. 

An introduction to evolution

Equine_evolution

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Good introduction from BBC Earth: How do we know evolution is real?

Evidence for evolution:

Tree of Life Resources:

YouTube Videos:

Patterns of Evolution

honeycreepers

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Speciation: Due to natural variation between individuals, selection pressure, “survival of the fittest” and favourable traits being passed on to offspring over many generations, new species are formed. Biologists refer to allopatric (geographical), sympatric (same location and habitat), and parapatric (habitat differences) speciation.

Divergent Evolution: Over time, due to selection pressures, sub-species or species become less and less alike, as they become better adapted to their niche. Adaptive radiation (below) is a specific type of divergent evolution. The human foot and the foot of a chimpanzee is an example – they are quite different (divergent), although they evolved from a common ancestor, due to the differing habitats of the upright walking man, compared to the knuckle-walking chimpanzee.

Adaptive Radiation: The process by which organisms change over generations to fill different niches, especially when changes in the environment make new resources available. Charles Darwin famously documented the different beak shapes of finches on the Galapagos Islands, which he postulated had arisen form a common ancestor. Above, you can see the variations of honeycreepers from the Hawaiian islands.

Convergent Evolution: In this form of change over time, different species begin to look more alike, despite having no recent common ancestor. Analogous structures develop, that have the same form and function, but were not present in the most recent common ancestor. Examples include flying insects, birds and bats, who have all developed wings as a solution to escaping from predators or finding more food and mates. Hedgehogs and echidnas are a good example of convergent evolution.

Parallel Evolution: Parallel evolution is similar to convergent evolution, in that different organisms display similar characterisitics, but tend to be more closely related. So, gliding frogs for example, evolved in parallel from multiple types of tree frog. Some examples that are closer to home include the Tasmanian tiger and the European wolf; the flying squirrel and gliding possums and marsupial and placental moles/mice.

More about patterns of evolution:

Evidence for Evolution

Haeckel_drawings

 

Image Source – Haeckel’s drawings

What evidence supports the theory of evolution? – some good questions here!

This interactive animation, “Evolution in Action” outlines the evidence for evolution and gives an opportunity for students to particpate in a simulated natural selection experiment.

Origins of Life

Screen Shot 2014-08-12 at 6.58.02 PM

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1. Download the student worksheet from Ages 16-19: Highlighting Important Stages in Evolution

2. Watch the “Tree of Life” video, narrated by David Attenborough

3. Click on “Interactive” to view the “Tree of Life” Interactive timeline

4. Answer the questions on the student worksheet.

Other Resources:

What does it mean to be human?

three_skulls

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Have you ever wondered what makes us different from other animals? Why Homo sapiens appear to dominate the earth, altering the landscape and using vast amounts of energy compared to other species? The story might have began around six million years ago, when the primate lineage between humans and chimpanzees branched; in other words, we didn’t evolve from chimpanzees, they are like distant cousins, with a common ancestor six million years ago. A recent non-fiction book by psychologist Thomas Suddendorf, “The Gap – The science of what separates us from other animals” distills two traits that appear to account for most of the ways in which our minds appear quite different from other animals – the ability to cast our mind back and forward, imagining different scenarios and our drive to communicate with others, linking our minds together. I have only just started it, but so far it is fascinating and easy to read.

On Monday we had another terrific Polycom session with Tony and Frazer from the Gene Technology Access Centre. The session focussed on the characteristics of seven fossil skulls – in fact, half-scale models of skulls, including:

  • Homo sapiens (human)
  • Homo habilis
  • Homo erectus
  • Homo neanderthalensis
  • Australopithecus afarensis (also known as ‘Lucy’)
  • Gorilla gorilla
  • Pan troglodytes (chimpanzee)

We looked carefully at the models and tried to order and classify them based on the following characteristics:

  • Presence or absence of pronounced canine teeth
  • Presence or absence of a sagittal crest (presence indicates exceptionally strong jaw muscles)
  • Protruding jaw
  • Brow ridges (subtle or pronounced)
  • Presence of temporal lines
  • Cranium capacity (an indication of brain size – measured in millilitres)
  • Location of the foramen magnum – where the spinal cord passes through the skull to attach to the brain (using a ratio) – this indicates if the specimen is quadrupedal or bipedal.

If we consider the Homo sapien skull to be most advanced, it appears that the brain case has increased in size and become smoother, with a more rounded forehead and the face has become flattened, with a less pronounced jaw.

Habitats, Environment and Survival

Otway forest

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This chapter of work is about habitats and the factors that affect the survival of organisms in their environments. You will learn about biotic (living) factors – predators, competitors, pathogens, parasites – and abiotic (non-living) factors – temperature, wind speed, pH, atmospheric gases, turbidity, salinity, solar radiation etc. You will also learn about niches and resource use graphs. Match some Australian species to their habitats at DECC.

Living organisms survive in their environments due to structual, functional and behavioural adaptations. Evolution is the process by which living organisms have changed over thousands of years to become more suited to their environments. Google ‘evolution’ and you will find an enormous selection of contradictory articles confirming or condemning “The Theory of Evolution”, first proposed by Charles Darwin in 1859.

To summarise Darwin’s Theory of Evolution;
1. Variation: There is variation in every population.
2. Competition: Organisms compete for limited resources.
3. Offspring: Organisms produce more offspring than can survive.
4. Genetics: Organisms pass genetic traits on to their offspring.
5. Natural Selection: Those organisms with the most beneficial traits are more likely to survive and reproduce.

Natural Selection Animations

peppered moth

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Natural selection is the important process that results in changes in populations over time. All the structual, functional and behavioural adaptations we have discussed over the past few months have evolved as a result of natural selection. However, because the effects of natual selection can only be seen over many generations, it is difficult to visualise. There are a number of computer simulations that allow us to visualise natural selection. The Peppered Moth Simulation, from the Biology Corner, uses a well known example of a case study of natural selection. The Biology in Motion lab uses more stylized images for it’s Evolution Lab.

Darwin’s 200th Birthday

Image Source – The United Kingdom 10 pound note.

This year many scientists are celebrating Charles Darwin’s 200th birthday. Darwin is famous for his book, “The Origin of Species” which was a revolution in biology and controversial in it’s day for the theory that species could evolve over generations to form new species – and that humans had evolved from an ape-like ancestor! Darwin was the first scientist to propose this theory and provide a simple mechanism – survival of the ‘fittest’  – that could explain how it works. Even before chromosomes and genetics had been discovered, he proposed that there was some ‘hereditary factor’ that was passed through generations and conferred characteristics that made individual organisms more or less likely to survive, breed and pass on those characteristics to their offspring.

Catalyst is celebrating Darwin’s 200th birthday with a special edition, that includes interviews with famous scientists, articles about DNA and missing fossil links and archives of related stories. Read a biography of Charles Darwin from the BBC and find out more at “Darwin – the Genius of Evolution“.