Powerpoint: Fungi General Characteristics

Learning Objectives 

• Identify the characteristics of Kingdom fungi
• Explain the role fungi play in the ecosystem
• Identify the common characteristics of Kingdom fungi

Take a piece of paper and draw the first thing that comes to mind when you think “fungi”.
It may look something like this:

If you drew something like this, than you’re thinking like google (these are  3 of the first pictures when doing a google search of “fungi”). Most of us consider fungi to be synonymous with “mushroom”, of the club shaped fruiting bodies above. However, mushrooms make up only a small part of the kingdom. Almost all the things we consider “mushrooms” belong to one of five fungi phyla (phyla Basidomycota). Not only that, the visible mushrooms here are only the tip of the iceberg. Where a mushroom sprouts, you could be standing on meters, sometimes even miles, of fungi hidden underground. The largest living organism in the world is thought to be the honey fungus in blue mountain, Oregon, hiding 2.4 miles of monstrosity underground (article below). This is one of the reasons fungi are called the “hidden kingdom”: hidden from view, under-appreciated, but ever present and important in our livelihoods and the ecosystem.

http://www.bbc.com/earth/story/20141114-the-biggest-organism-in-the-world

• Fungi are one of three kingdoms (plus animalia and plantae) that are multicellular.
• Like Plants and animals, fungi are also eukaryotic, meaning it has a nucleus and other organelles, all membrane bound.
• Fungi have cell walls, usually made up of chitin (but not always)
• Like animals, but unlike plants, fungi are heterotrophic. That is, they depend on other organisms (organic material) for their energy. Therefore, contrary to popular belief, fungi are believed to be more closely related to animals than either kingdom are to plants.
  • Fungi do not ingest their food like animals do
  • Instead, they secrete digestive enzymes outside their cell walls and membrane.
  • The digestive enzymes break down the food into small pieces, which can then be absorbed through the cell walls and membrane
  • Essentially the whole fungi acts as a stomach and intestines, secreting enzymes and then absorbing them
• In the ecosystem, fungi act as major decomposers
• Other than yeast (unicellular), all fungi are made up of tiny filaments called hypae. The hyphae are usually tangled into a thick mass, called mycelium.
• Most fungi can reproduce sexually and asexually 

Powerpoint: Mitosis Meiosis

Learning Objectives 

• • Identify the products of mitosis and meiosis
  • Define haploid (N) and diploid (2N)
  • Identify if a cell is diploid or haploid
  • Identify the parts of the human body where mitosis and meiosis occurs
  • Describe (with an analogy) the process of sexual reproduction, mitosis and meiosis

In the following weeks, we will be exploring the multicellular, eukaryotic kingdoms: Fungi, Plantae and Animalia.  As multi-cellular organisms, cell division and sexual reproduction are critical life stages. As we will see, organisms have come up with some unique strategies for completing these processes.

To understand cell division and sexual reproduction in multicellular organisms it is important to first understand the processes of mitosis and meiosis. To familiarize ourselves with these terms, let’s take a look at human cell division and sexual reproduction and compare it with making airplanes (I’ll clarify in a minute).

Human Cell Division

Cell division in humans (and most organisms) occur via a process called mitosis.

Mitosis: process by which the nucleus of a cell is divided into two nuclei, each with the same number and kinds of chromosomes as the parent cell.

In mitosis, the cell is simply making a copy of itself. No new DNA combinations are being formed, nothing fancy. The product is two identical cells.

1. The DNA replicates (makes an identical copy of all DNA in the cell)
2. The DNA is pulled apart (each cell has one copy of all DNA)
3. Identical daughter cells form

Building Airplanes Analogy: Now lets compare human cell division to airplanes. DNA is often called the “blueprint of life”, just like the blueprint of an airplane is used to build the airplane. So if we were to compare mitosis to airplane blueprints…

1. Two airplane blueprints are replicated (copied onto another sheet of paper)
2. Each of the two airplane blueprints now make one complete organism

Wait! You say. That doesn’t make any sense. Why would there be two airplane blueprints? Shouldn’t it just be one? As it turns out, in human cells, we also have two complete blueprints on how to make a human – one from the biological mother and one from the biological father. Because human beings (and most animals) have two complete “blueprints” in their cells, they are known as diploid organisms. 

Diploid: organisms which have two copies of DNA, one inherited from each parent.
Haploid: cells or organisms which have only one copy of DNA. (e.g. human sperm and egg cells)

Interestingly, there are many organisms (particularly in the plant kingdom) that have more than two copies of DNA. For example, grocery bought strawberries can have eight copies of DNA! Our seedless bananas and watermelons have three copies of DNA.

Human Gametogenesis (creation of sex cells)

Humans, as with most if not all animals, most plants and some fungi, undergo sexual reproduction.

Sexual reproduction: process in which two cells, normally from different individuals, unite to produce the first cell of a new organism.

In order for sexual reproduction to happen, gametes must be created. Gametes are special cells that contain half the genetic information that most cells have. Females gametes are eggs, male gametes are sperm. Each of these have half the genetic information that a cell would have. When the two are combined, a zygote (the first cell of a multi-cellular organism is formed). Then mitosis occurs, the cells duplicate until the trillions of cells that make up your body is formed.

Because the gametes all have only one complete copy of DNA, they are referred to as N, or haploid. All other cells in your body other than sperm and egg however, have two complete copy of DNA. Therefore, we refer to them as 2N, or diploid.

Therefore, whereas Mitosis creates more of the same cells, meiosis creates cells with half the genetic information cells normally have. Combining the gametes of two different organisms produces an entirely new organism, which is the whole point of sexual reproduction: to create something new instead of more of the same.