A Local Ecosystem, Patterns in Nature,Life on Earth,The Australian Biota

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Topic 1:

A Local Ecosystem

  • Compare the abiotic characteristics of aquatic and terrestrial ecosystems

Organisms that live in aquatic and terrestrial have a very different apperence (morphology) and way of functioning (physiology). Terrestrial animals have support for living out of water and for transport on land.

  • Identify the factors determining the distribution and abundance of a species in each environment

A population will continue to grow in abundance until it is restricted by a limiting factor. A limiting factor is a rescource that is in short supply and so restricts the growth of a population. Limiting factors include: lack of space, preditors, disease, competition for food between members of the same or other species, physical factors eg whether conditions, availability of water and light etc. The distribution of plants in a marine environment is limited to the area where light penetrates for photosynthesis to occur.

  • Describe the roles of photosynthesis and respiration in ecosystems

Producers capture light through the process of photosynthesis and is used to combine carbon dioxide with water, making oxygen and forming carbohydrates such as glucose. Glucose is what provides energy to the consumers which is vital for growth and reproduction. In addition, photosynthesis produces oxygen, which is essential for the process of respiration. This is important in ecosystems so that energy can be delivered to cells that can be used in growth, development and reproduction.

  • Identify uses of energy by organisms

Energy from respiration powers all the processes of life. Some energy is released as heat, which can help keep the animal warm and maintain optimal temperatures for the chemical reactions that occur in cells. Other activities that require the energy from respiration include, growth, muscle contraction and movement, synthesis of complex chemicals, repair of damaged cells, reproduction.

  • Identify the general equation for aerobic cellular respiration and outline this as a summary of a chain of biochemical reactions

Glucose + Oxygen → Carbon Dioxide + water + energy

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

Energy-releasing respiration can be called aerobic respiration because it takes place in the presence of oxygen and within cells. It is also referred to as cellular respiration. Glucose and oxygen are converted to carbon dioxide and water and water, with the release of energy.

  • Examine trends in population estimates for some plant and animal species within an ecosystem

The number in a population may vary throughout the year because eof seasonal changes. For example wales migrate during winter in search of warmer shores. Also many plants die during winter and then recover over spring, so both the wale and plants would have different population trends throughout a year.

  • Outline factors that affect numbers in predator and prey populations in the area studied

Predator and prey population numbers are closely related and potentially unstable. If there is too much predation, the number the number in each prey population will decrease, or one or more prey species may disappear altogether. These changes are followed by a decrease in the predator population, or the predators will attack a different prey species. If a population of predators is removed from an ecosystem, the prey population may multiply rapidly, leading first to habitat destruction and then to a reduction in the number of prey.

  • Identify examples of allelopathy, parasitism mutualism and commensalism in an ecosystem and the role of organisms in each type of relationship

Allelopathy occurs in plants. It is where a plant excretes a chemical which may be beneficial or harmful to other plants. Many Australian plants, such as casuarinas and eucalypts, produce allelochemicals the prevent competition from other plants.

Parasitism is a close relationship that occurs between two species. One species, the parasite is benefited by the relationship while the other, the host is disadvantaged. An example of this includes the tapeworm living inside a mammal. The tapeworm is protected and is supplied with food, while the mammalian host suffers from a loss of nutrients.

In mutualism, both organisms benefit from the relationship. Lichen is an example of a close mutualistic relationship between an alga and a fungus. The alga produces food through the process of photosynthesis. The fungus provides a place for the alga to live.

Commensalism is a form of symbiotic relationship in which neither organism is disadvantaged, but one may be advantaged. For example, a shark swimming with a remora fish may not be advantaged but the remora can feed on any scraps that the shark misses.

  • Describe the role of decomposers in ecosystems

A large part of the recycling of matter which occurs in an ecosystem is carried out by decomposers such as bacteria and fungi. When organisms die of produce wastes, they are broken down into simpler compounds by decomposers. These simpler compounds can then be take up from the soil by plants and reused. Without decomposers, there would be a build up of dead organisms and nutrients would remain locked within them.

  • Explain trophic interactions between organisms in an ecosystem using food chains, food webs and food pyramids of biomass and energy

Trophic interaction is the term used to describe the interaction where one organism eats another. They also show the flow of materials and energy through and ecosystem. Trophic interactions can be represented graphically by drawing a food chain. Food chains show what organisms eat. Food chains begin with a producer or autotroph. The next level on the food chain is a consumer or heterotroph and is called the first order consumer. First order consumers are always herbivores. The second order consumers and so on are carnivores.

Food webs are more complex than food chains because they show that predators are not limited to one prey species and they indicate that some organisms are consumed by a variety of predators. In many cases a species may be a preditor to one species and the prey to another. Food webs often include decomposers. Food chains and food webs are useful for illustrating the trophic interactions that occur between organisms in an ecosystem, but they give no indication of the relative abundance or size of organisms. Food pyramids are models that can take account of how biomass (total mass taking up the organisms in a population) and energy vary in trophic interactions. The biomass of a trophic level is estimated by finding the dry weight of an organism in the trophic level then multiplying by the total number of organisms in the population. Biomass for different trophic levels is compared in a biomass pyramid to see how the quantity of matter in living things changes along a food chain. The base of the pyramid represents the matter in producers. The next level shows the biomass of first order consumers and so on to the top of the pyramid.

A pyramid of energy depicts the total energy in trophic levels and shows how energy is lost along a food chain. Energy loss is repeated along a food chain and a energy pyramid is used to represent this.

  • Define the term adaptation and discuss the problems associated with inferring characteristics of organisms as adaptations for living in a particular habitat

Adaptation can be defined as any feature of an organism that increases its chances of survival in the environment in which it lives. These features are built up in a species over a long period of time through the selective pressures placed on the species by environmental factors. There are problems in inferring (assuming) that all useful features have developed as adaptations to a particular environment as it may have always obtained this feature or gained it for a different reason for example the iis is a wetlands bird that has become common in cities eating out of city drains and garbage bins. By looking at its curved beak it could be claimed that it has become perfectly adapted to the urban environment when in fact it is only a recent arrival.

  • Identify some adaptations of living things to factors in their environment

There are different types of adaptations including structural, physiological and behavioural. Structural adaptations are the anatomical features of an organism that assist it to survive. For example a fish has a streamlined body which enables it to move freely with reduced friction through water. Physiological adaptations are metabolic features of an organism that assist it to survive. For example, a fish produces mucus which covers its body and allows water to flow over its scales. Behavioural adaptations are things that an organism does (or doesn’t do) that assist it to survive. For example, a fish swims into seagrass beds to avoid detection by a nearby preditor.

  • Identify and describe in detail adaptations of a plant and an animal from the local ecosystem

  • Describe and explain the short term and long term consequences on the ecosystem of species competing for resources

Competition can be for food, nesting sites, mates, water, light or shelter.

Competition for lack of food resources can often resulting in death which can ultimately affect the abundance of a species. Often there is competition between members of different species. Over the short term, if one species has an advantage over another it will limit the growth of that population. Over the long term, competition may lead to the extinction of the disadvantaged species.

  • Identify the impact of humans in the ecosystem studied

Human impact comes from; increased hard surface areas leading to greater run off, fishing and bait collection, which reduces the numbers of of target species, pollution by fertilisers and pesticides from garden run off, pollution of local bodies of water called eutrophication  where nutrients (often sewerage) cause excessive plant growth uses up all the oxygen in the water and kills most plants and animals, use of landfill for house and parks, introduction of species, increased frequency of fires.

Topic 2:

Patterns in Nature

The Theory of Spontaneous Generation

  • Living things come to existence from non-living things
  • Developed in the 17th Century
  • That some animals such as warms and frogs could spontaneously emerge from mud or water, or that maggots develop from rotting meat
  • In the 19th Century this theory was proven wrong when Luis Pasteur’s experiments proved that micro organisms arose only from other micro organisms.
  • As a Result the “Cell Theory” was developed which emerged the scientific basis for the “germ theory of infections”

  • Outline the historical development of the cell theory, in particular, the contributions of Robert Hooke and Robert Brown

The Cell Theory

  • The Cell Theory was first created in 1839 by German biologists Mattias Schleden and Theodor Schwann.

The Cell Theory

  1. Cells are the smallest units of life
  2. All living things are made up of cells

In 1858 Rudolf Virchow added that:

  1. All cells come from pre-existing cells

Robert Hooke

Robert Hooke had a significant effect in the history of science. In the 17th Centaury, Hooke became the first person to record his study of cells through the use of his microscope.

Hooke was the first person to describe cells and he described them to look like honeycomb and that the ‘pores’ of cells consisted of many little boxes. He first identified and named the cell.

Robert Brown

Robert Brown also had significance in his discovery of cells, and the development of the cell theory. His work in 1831, made him the first person to describe the cells nucleus as a large body found inside the cell, he also was the person to give the nucleus its name.

     1600

        First microscope

1665

Robert Hooke further developed microscope

1672

Marcello Malpighi stated that all plants are built of chambers

1685

Anton Van Leeuwenhoek discovered bacteria in saliva

1831

Robert Brown first described the nucleus

1858

Rudolf Virchow said that in order for life to come about there must be a cell that was there before the current cell

1880

Walther Flemming first described mitosis

1960-Today

Xray microscope developed and used to observe cells

  • Describe evidence to support the cell theory

By the 1880’s, the accepted idea was that plants and animals were composed of globules, called cells, and formless material. Brown had enhanced this idea by describing nuclei in cells or orchid plants. This idea as then extended by two German biologists.

In 1838, Matthias Schleiden suggested that cells were the basic structural unit of all plant matter. Matthias Schleiden and Theodor Schwann both agreed that both plant and animal tissues have a cellular organism. They then studied cells and concluded that all living things consist of one or more organised structures that are called cells or of products of cells, and that cells are the basic functional unit of life. Through Rudolf Virchow’s studies a third point about cells were made. He proposed that new cells come from existing cells. That is, where a cell arises, there must have previously existed just as an animal can spring only from an animal.

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In 1862, Luis Pasteur carried out experiments that conclusively disproved the old idea of spontaneous generation, and supported the view that new cells are produced by existing cells.

  • Discuss the significance of technological advances to development in the cell theory

Technological advances around the time of the development of the cell theory lead to the discovery of chromosomes and further discovery of the nucleus. Further technological advances in 1933 when the electron microscope was invented let more detailed observations of all structures to be made. Laser scanning and 3D imaging software have improved our knowledge of cell and ...

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