Tag Archives: biology

What does it mean to be human?

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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.

Class of 2011

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biology2011classx450

These are the five lovely students in our Year 11 Biology Class this year.  We are starting with Unit 1:  Cells in Action. In addition to completing the Chapter 1 Review questions we will be doing the following activities:

iCell_app 
Use the iPod Touch app “iCell” by HudsonAlpha Institute for Biotechnology to review the structure and function of organelles within plant, animal and bacterial cells.

cells_alive
Use the “Cells Alive” website to learn about the relative sizes of different objects veiwed under a microscope, as well as the study the models of plant, animal and bacterial cells. Biology Corner has an excellent website, with an internet lesson and worksheet that can be printed. You will look at computer models of cells, learn the functions and the descriptions of the cells and their components.

What is Ecological Succession?

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sand_dunes

What is ecological succession? This is the answer from Rolcam at the Ask Me Help Desk.

“Changes in communities occur over time in a process called ecological succession. This process occurs as a series of slow, generally orderly changes in the number and kinds of organisms that live in an area take place. Differences in the intensity of sunlight, protection from wind, and changes in the soil may alter the kinds of organisms that live in an area. These changes may also alter the number of populations that make up the community. Then, as the number and kinds of species change, the physical and chemical characteristics of the area undergo further changes. The area may reach a relatively stable condition called the climax community, which may last hundreds or even thousands of years. ”

The first plants that germinate in an area are called ‘pioneers’ and are usually grasses or ground covers. Weeds are effective pioneers on roadside verges for example, where they colonise bare round and provide shelter for other plants to grow.

“Ecologists distinguish two types of succession–primary and secondary. In primary succession, organisms begin to inhabit an area that had no life, such as a new island formed by a volcanic eruption. Secondary succession takes place after an existing community suffers a major disruption–for example, after a climax forest community is destroyed by fire. In this example, a meadow community of wild flowers and grasses will grow first, followed by a community of shrubs. Finally trees will reappear, and the area will eventually become a forest again. Thus, the forces of nature ultimately cause even climax communities to change.”

Do the following situations demonstrate primary or secondary succession?

  • Growth of grass trees after an intense bushfire in the Grampians National Park
  • Pisonia sp. forest that grows on a coral cay, Heron Island on the Great Barrier Reef
  • Open Acacia and Eucalyptus woodland that grows after volcanic action at Mt Eccles National Park
  • Sand dune vegetation that grows at Griffith’s Island, Port Fairy
  • Fern forest growing after glacier action in New Zealand

Classification

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Melbourne Museum - Wild Exhibit

Image Source Wild Display at the Melbourne Museum.

It is important for biologists to classify living organisms so species can identified and organised into groups according to their common features. The National Science Foundation’s “Tree of Life” project estimates that there could be anywhere from 5 million to 100 million species on the planet, but science has only identified about 2 million. Of these two million, the IUCN red list estimates that over 17, 000 species are in one form or another threatened with extinction today. So as fast as taxonomists are identifying new specimens, we are losing known species to habitat loss, introduced pests, pollution, overkill and climate change.

We often hear about threatened extinction of some conspicuous animals or plants, but it is usually not realized that each large species is host to many species of parasites, some of them specific to that host species and therefore doomed to extinction with it. The human species, for example, is host to far more than 100 parasite species, quite a few of these only found in humans. Species have not evolved in isolation – think of the co-evolution of flowering plants and their pollinators, toxic plants and their predators and animal camouflage.

This Chapter of work includes the Linnaean system of naming organisms, binomial nomenclature (Genus species system), heirarchical grouping (Kingdom, Phylum, Class, Order, Family, Genus and Species), dichotomous keys and cladograms. This site has some interesting mnemonics to remember biological terms for your upcoming exams.

Revision of Unit 1: Cells in Action

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animal cell cake

This is a model of an animal cell made from cake showing the different organelles of a typical cell. The nucleus is shown by the freckle, mitochondrian was shown by the purple jelly beans, the lysosomes were the yellow jelly beans, the centrioles was the musk sticks which were then placed on the cytosol (icing), the vaccuole was shown by two freckles placed upside-down, the endoplasmic reticulum was made with yellow snakes and the rough endoplasmic reticulum was made with yellow snakes with 100’s and 1000’s laces on top to make the ribosomes and for the golgi compex was made by placing a pink snake on the icing.

This activity was enjoyed by the year 11 biology group. Making a model of a cell meant that we could relate to what a real one looked like. This made it easier to remember the names of parts of the cell and what their function was.

Chapter 1 (Cell Discovery and Exploration): Stephanie and James

Chapter 2 (Cell Structure and Function): Chris and Melissa

Chapter 3 (Composition of Cells): Charlotte and Catherine

Chapter 4 (Cell replication – Mitosis and Meiosis): Monique and Chloe

Classification of Living Organisms

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We are all relatively familiar with the five classes of vertebrates (mammals, birds, reptiles, fish and amphibians), but less familiar with species that account for about 97% of all known animal species – the invertebrates – or animals without backbones. The arthropods (including all insects, spiders and crustaceans) probably outnumber all other animals on earth, yet most of them are very small and easily overlooked. Invertebrates are found in every conceivable type of habitat, but they are most plentiful in the oceans, which is where animal life first arose. This week we will look at how living organisms are classified, some of the characteristics used in taxonomy and how different groups are related according to their evolution.

We often hear how many species are becoming extinct each year – less often we hear about the new species that have been discovered. In 2007, over 18,000 new species were described. This year a naturally decaffeinated coffee plant, a tiny seahorse and bacteria that thrive in hair spray have been discovered. Article from Scientific American, “Top 10 new Species“,  here.

I will be away at the school cross country on Tuesday, 26th May, so you are asked to complete Activity 8.1 in your practical manuals – “A key to sorting snakes”, about using a dichotomous key to extract information and identify various species. Please leave me a comment on this post to let me know how you went and waht you learnt.

A simple introduction to Classification from KidsBiology.com

Excellent site for Classification of Animals including characterisitics of each of the Phyla, images and links.

Go to ARKive for a growing collection of information, images and videos about all our magnificent organisms on earth. There is a collection of education resources, which includes downloads for different age groups. We will be looking at the ARKive Classification Resource in class on Wednesday, 27th May.

A more in-depth introductionabout the Linnaen Binomial System of Nomenclature and Principles of Taxonomy. 

Identify eight marine creatures from Chesapeake Bay, near Baltimore, USA using a dichotomous key.

Table of the Five kingdoms.

Excellent Glossary of terms.

Flashcards for Introduction and taxonomy.

Excellent interactive “Essential Study Guide” from McGraw Hill

Heart pumps out new cells!

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Swedish scientists have used radioactive carbon-14 to show that between 0.5 and 1.0% of heart cells regenerate each year, depending on age. Read more here.

We were talking about bees in class during the last week of term – I happened upon this interesting article from the Scientific American – “Plan Bee: As Honeybees Die Out, Will Other Species Take Their Place?”

I’ve also added a few more resources to the Free Stuff! column on the RHS – Check out “Biology Q and A” for over 1800 questions and answers about Biology.