Biology

Nutrition in Amoeba

Nutrition in Amoeba:
Protozoan protests carry out holozoic nutrition through intracellular digestion.
(i) Ingestion:
Some protests can ingest food particle from any point on the surface (e.g., Amoeba) while others have fixed points for the same (e.g., Paramoecium). Protozoans like Amoeba capture food with the help of temporary finger-like processes called pseudopodia. Protozoans like (Paramoecium have small hair-like processes called cilia.) Beating of cilia creates current in water that pushes food particle through cytostome or cell mouth. The process of ingestion of solid food particle by a cell or unicellular organism is called phagocytosis.


As soon as Amoeba comes in contact with a food particle or prey, it throws pseudopodia all around the same. The tips of encircling pseudopodia fuse and the prey comes to lie in a vesicle or phagosome. This method of intake of food is called circumvallation. Amoeba can also ingest food by other methods like import, circumfluence and invagination.

Laboratory Skills: Scientific Method

Vocabulary: bias, conclusion, control, control group, data, dependent variable, experimental design, experimental group, hypothesis, independent variable, peer feedback, peer review, problem, results, scientific method, theory, variable, variable group

Scientific Methods

Scientific explanations are developed using both observations and knowledge about what people already know. All scientific explanations are tentative explanations of phenomena and are subject to change. Good science is a combination of questioning, experiments, evidence, logical argument, ingenuity, and skeptical peer review. The scientific method and good scientific technique can be used in every day decision making, as well is in scientific investigation. Scientific literacy involves the use of science and it knowledge so that it can be applied in everyday life, particularly in relation to the health, commercial, and technological claims.

Scientific explanations are built by combining evidence that can be observed with what people already know about the world. This learning about the historical development of scientific ideas provides a better understanding of science, as well as the relationship between science and society. Personal values are also essential to making effective and ethical decisions about the application of scientific knowledge.

Developing a Research Plan

A procedure provides a description of how to organize a scientific experiment to test a hypothesis. The idea for research can be refined through library investigations, including the use electronic information such as e-mail and the internet, retrievals and reviews of scientific literature, and through peer feedback obtained from review and discussion of the problem, hypothesis, and procedure for experimentation before it is conducted.

Development of a research plan involves researching background information and understanding the major concepts in the area being investigated. Recommendations for the methods used for studying the problem, methods of study, technology selection and use, choice and use of proper equipment, and appropriate safety precautions should be included in the design of the experiment.

Scientists must follow certain steps in their attempt to solve problems. These steps are often referred to as the scientific method. The first step in the scientific method is to form a problem or question to solve. The formulation of the problem to be studied often requires as much work as the scientific experiment itself. The inquiry involved in the initial research of the problem involves asking questions and locating, interpreting, and processing information from a variety of sources. These other sources could include library information, information from other scientists, and the internet. When writing a scientific paper, this problem should be stated in the form of a question.

After the scientist has decided upon the problem to be researched, the second step of the scientific method is to form a hypothesis about the problem. This is an prediction of the possible outcome of an experiment based upon prior research and observation by the scientist. Hypotheses are widely used in science for determining what data to collect and as a guide for interpreting the data which is collected. The research plan for testing a hypothesis requires careful planning to avoid bias in this experiment. This plan should include repeated trials, large sample sizes, and objective data-collection techniques. As in deciding upon the problem to be researched, the development of a research plan involves researching background information and understanding the major concepts in the area being investigated. Recommendations for methodologies, use of technologies, proper equipment, and safety precautions should also be included in the design of the investigation. Well designed hypotheses are valuable, even if they turn out not to be true, because they may lead to further investigation and will direct the data collection activities in the experiment.

The third step of the experiment is the experimental design which tests the hypothesis. This procedure should clearly indicate the materials to be studied in the experiment and the measurements to be taken. There must be two groups included in the experimental procedure. The control group contains all the parts of the experiment except the factor being tested. The variable group contains all the factors of the control group as well as the one factor that is being tested. This is sometimes also called the experimental group. A well designed procedure contains only one variable. The control group acts as a basis to compare with the variable group.

There are two types of variables in an experiment. The independent variable is the variable which is changed or manipulated by the investigator. The dependent variable is the variable which is influenced by changes in the independent variable. This is what is measured in the experiment. The example which follows will illustrate some of the information involved in the design of a procedure.

The Scientific Method in Action

The following question about the scientific method appeared on the June 2001 New York State regents examination:
You are the head of the research division of the Leafy Lettuce Company. Your company is experimenting with growing lettuce using hydroponic technology. Hydroponic technology involves growing plants in containers of growth solution in a greenhouse. No soil is used. The growth solution that the company uses contains water, nitrogen, and phosphorus. The company wants to know if adding iron to this formula will improve lettuce growth.

• State a hypothesis to be tested in the new experiment
• State how the control group will be treated differently from the experimental group
• state what type of data should be collected to support or refute the hypothesis
• A good hypothesis relates the independent and dependent variables of the experiment together. In this experiment, a good hypothesis could be that the addition of iron to the growth formula will improve the growth of the lettuce. (Note that the hypothesis is phrased as a statement, not a question.)

The control group is not given the variable being tested. The experimental or variable group would receive the iron added to its growth solution, while the control group would not.

The type of data collected involves how the independent variable (the kind of growth solution) influences the dependent variable which is the growth of the lettuce. The experimenter would want to collect precise measurement data, such as how much more the lettuce grew in cm. or gained weight in grams.

The fourth step of the experiment is to organize the results or data collected. This may involved the use of data charts, graphs, tables, or drawings. When a variable is manipulated in an experiment, the data must include the changes in the independent and dependent variables. The scientist will then review these results. This often leads to new hypotheses being formed and additional scientific investigation.

The final step of an investigation may be to form a conclusion based upon the data. Using the trends in your experimental data and your experimental observations, the conclusion should try to answer the original problem. A conclusion should be able to assess the correspondence between the predicted result contained in the hypothesis and the actual results, and reach a conclusion as to whether the explanation on which the prediction was based is supported. No assumptions can be made about the results of the experiment past the one and only experimental factor that is being tested.

It is critical for the investigator is to communicate the results with others to allow for peer review of the investigation by other scientists. This can be done in a scientific journal, through the Internet, or by other means.

Peer Review and Repeatability of Experiments
One assumption of science is that other individuals could arrive at the same explanation if they had access to similar evidence. Scientists must make the results of their investigations public. The experimenter should describe the investigations in ways that enable others to repeat the investigations.

Scientists use peer review to evaluate the results of scientific investigations and the explanations proposed by other scientists. They analyze the experimental procedures, examine the evidence, identify faulty reasoning, point out statements that go beyond the evidence, and suggest alternative explanations for the same observations. Claims should be questioned if the data are based on samples that are very small, biased, or inadequately controlled or if the conclusions are based on the faulty, incomplete, or misleading use of numbers. The results of an experiment should be questioned if fact and opinion are intermingled, if adequate evidence is not cited, or if the conclusions do not follow logically from the evidence given. Accepting the results of any scientific inquiry involves making judgments about the reliability of the source and relevance of information obtained. Scientific explanations are accepted when they are consistent with experimental evidence and when they lead to accurate predictions about further extensions of the investigation.

Assessing Experimental Results

The results of a scientific experiment must be presented to the public and peers (other scientists) before they can be accepted. An assumption of science is that other individuals could arrive at the same explanation if they had access to similar evidence. The procedure used in conducting the experiment must be stated precisely enough to allow other scientists to perform the experiment and determine whether the results obtained are repeatable. The written report for public and peer study should describe the proposed explanation, literature reviewed, the research carried out, its result, and any suggestions for further scientific research.

Scientists use peer review to assess the results of scientific investigations and explanations proposed by other scientists. It is important the other scientists critique original research conducted by scientists in this manner. They analyze the experimental procedures, examine the data obtained in the experiment, and identify faulty reasoning in assessing the data. Peer review also leads to scientists pointing out any conclusions that go beyond the evidence obtained. They also may suggest alternative explanations for the same observations.

This peer and public discussion may lead to revisions of the explanation provided by the research and lead the scientist to additional research related to the original problem being investigated. Therefore, hypotheses are valuable, even if they turn out not to be true, because frequently they lead to further investigation.

Questioning Claims
The claims made in a scientific investigation should be questioned if the data are based on very small samples. Claims made by individuals having bias must be questioned. Bias means to have an opinion about the experimental results before the investigation which will lead to the misinterpretation or manipulation of the data obtained in the experiment. An improperly controlled scientific experiment must be questioned. The experiment should contain at least one clear control and one independent variable. The conclusions obtained in an experiment must be questioned if they are based on the faulty, incomplete, or misleading use of numbers. Fact and opinion must not be intermingled in a proper scientific experiment. The results of the experiment must cite adequate evidence and have its conclusion following logically from this evidence.

Theories
All scientific explanations are tentative and subject to change or improvement. Each new bit of evidence can create more questions than it answers. This leads to increasingly better understanding of how things work in the our world. When consistency is obtained in repeated scientific investigations of a problem the hypothesis becomes a theory and provides a set of ideas which explain a class of phenomena. A theory is then a framework within which observations are explained and predictions are made. Well-accepted theories are ones that are supported by different kinds of scientific investigations often involving the contributions of many individuals from different disciplines.

Human Biosphere/Influence

Vocabulary: biodiversity, monoculture, greenhouse effect, endangered species, exotic/invasive species, acid precipitation, global warming, CFCs, SEQR, biodegradable

Biodiversity

Due to evolution, there is a great number of different organisms which fill many different roles in ecosystems. The number of different organisms in an ecosystem is called biodiversity. Increased biodiversity increases the stability of the ecosystem. Biodiversity also ensures the availability of diverse genetic material that may lead to future discoveries with significant value to humans. As diversity is lost, potential sources of these materials for these discoveries may be lost with it. A great diversity of species provides for variations which increase the chance that at least some living things will survive in the face of large changes in the environment.

Biodiversity
As a result of evolutionary processes, there is a diversity of organisms and a diversity of roles in ecosystems. Biodiversity refers to the differences in living things in an ecosystem. Increased biodiversity increases the stability of the ecosystem as it provides for more genetic variation among species. A great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.

Human Influences on Biodiversity

When humans alter ecosystems either by removing specific organisms, serious consequences may result. Human beings are part of the Earth’s ecosystems. Human activities can, deliberately or accidentally, change the equilibrium in ecosystems. Humans are destroying other species as a result of population growth, consumption, and technology. Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is especially threatening current global biodiversity.

An example of a human activity which has decreased biodiversity is the use of monoculture in modern agricultural practices. Monoculture involves planting one variety of a species over a huge area. This leaves this area more vulnerable to predation or disease and the loss of many or all species.

Uses of Biodiversity

In addition to the aesthetic beauty added to the world by many different organisms, biodiversity also ensures the availability of a rich variety of genetic material that may lead to future agricultural or medical discoveries with significant value to humankind. As diversity is lost, potential sources of these materials may be lost with it.

Interrelationships

The Earth has limited resources to support the organisms that live on it. Increasing human population numbers are putting great pressure on many of these limited resources and deplete those resources which can not be renewed. Many different natural processes occur within those ecosystems influencing humans. Some of these processes include atmospheric quality. soil generation and conservation, energy flow, the water cycle, waste removal and recycling. Human activities are altering the equilibrium involved in these natural processes and cycles. If these changes due to human activities are not addressed, the stability of the world’s ecosystems may irreversibly affected.

Technological Developments

Human activities which have harmed ecosystems have resulted in a loss of diversity in both living things and the nonliving environment. Examples of these changes include land use, the cutting of vast areas of forest, and pollution of the soil, air, and water. Another way humans have changed ecosystems in a harmful way is by adding or removing specific organisms to these ecosystems Our ever increasing demand for energy has impacted ecosystems negatively as well. Many environmental risks are associated with our use of fossil and nuclear fuels.

Many factors associated with human populations have influenced environmental quality. These include population growth and distribution on our planet, our use of resources, the ability of technology to solve environmental problems, as well as the role of economic, political, ethical, and cultural views in solving these problems.

Improvements

Individual choices and the actions of society can contribute to the improvement of our environmental problems. Our choices which must include an assessment of the risks, costs, benefits, and trade-offs of new technologies and continued human expansion. All changes and proposed improvements need to consider both the human and environmental impact of the change.

Interrelationships

The Earth has limited to resources to support populations of humans and other organisms. Our ever increasing human numbers is depleting many of our planet’s resources and placing severe stress on the natural processes that renew many of our resources.

Ecosystem Processes

Natural ecosystems are involved in a wide variety of natural processes influencing humans and other organisms. The activities of humans in the environment are changing many of these natural processes in a harmful fashion. Some of these natural processes and a brief description of a human influence on these processes is indicated in the table which follows.

Some Detrimental Human Activities

Humans are part of the Earth’s ecosystem. Human activities can either deliberately or inadvertently alter the balance of an ecosystem. This destruction of habitat, whether accidental or intentional, is threatening the stability of the planet’s ecosystems. If these human influences are not addressed, the stability of many ecosystems may be irreversibly affected. Some of the ways that humans damage and destroy ecosystems are indicated in the table below.

Technological Developments

Human technologies which degrade the environment result in a loss of diversity in the living and nonliving environment. Biodiversity refers to the differences in living things in an ecosystem. Many of our technologies and resource use practices have resulted in an irreversible loss of biodiversity.

Some examples of human activities which have negatively influenced other organisms include our land use practices and pollution. Excessive land use decreases the space and resources available to other species on the planet. Air, soil, and water pollution changes the composition of these environmental resources, making them harmful and unusable for other species and sometimes ourselves.

Endangered Species

Endangered species are those species which are threatened with destruction due to habitat destruction or other factors. Animals which were once endangered but are presently successfully reproducing and increasing their numbers are the bison, gray wolves and egrets. Other endangered animals which are currently responding to conservation efforts and beginning to make a comeback are the whooping crane, bald eagle, and peregrine falcon. Even with these successes, the future of many endangered species remains in doubt.

Exotic Species

The importation of some organisms have caused problems for native organisms. Organisms which are imported into an area from another region are called exotic species. Many examples of this are found world-wide. Some common examples of exotic species having negative effects would include the rabbits and deer which were imported into Australia. These exotic species won the competition with many native herbivorous marsupials and became nuisance species. The starling was brought into the United States from Europe. The starling has out competed many of our native songbirds. We also have alien invasive species which have caused problems in New York State. These include the plants such as the Water Chestnut, Eurasian Water milfoil, and Purple Loosestrife and animals such as the Alewife and Zebra Mussel.

Purple loosestrife is a plant native to Europe. It was brought to North America in the early 1800’s by immigrants who valued its beautiful purple flowers. It is now a serious pest of wetlands. Once purple loosestrife enters a wetland, it takes over. Common native wetland plants, such as cattails, cannot compete with purple loosestrife. Once these native plants are choked out, the wildlife that depends on them for food and shelter are also eliminated.

Use of Fossil Fuels

Fossil fuels are becoming rapidly depleted. The use of these fuels are adding to out air pollution problems. The search and demand for additional fossil fuel resources also impact ecosystems in a negative way. Industrialization has brought an increased demand for and use of energy.

One of the ways the increased burning of fossil fuels has had a harmful influence of the environment is by causing an increased incidence of acid precipitation.

How does Acid Precipitation occur?

Most acid rain influencing New York State is caused by sulfur dioxide and nitrogen dioxide pollution from the burning of fossil fuels in the Western and Midwestern United States. These gases combine with water vapor in the atmosphere and fall back to the earth over New York and the Eastern United States as acid precipitation.

Some Problems Associated With Acid Precipitation

• Destruction of limestone and marble monuments due to increased chemical weathering
• Acidification of aquatic ecosystems destroying the life in them
• Damage forests and other plants in a variety of ways

Our increased burning of fossil fuels and the release of excess carbon dioxide to the atmosphere associated with their combustion is also contributing to the Greenhouse Effect or global warming. It is believed the increase in level of carbon dioxide and some other gases is not allowing much infrared or heat radiation to escape the planet into outer space. This is causing our planet to slowly warm The graphs in the table below show the link between increasing earth carbon dioxide levels and the increase in global average temperatures.

Relationship Between Global Temperature and Carbon Dioxide Levels

Some Consequences of Global Warming

Rising sea levels and coastal flooding
Changed precipitation patterns which may result in droughts in some regions and increased levels of crop failure
An increase in insect borne diseases in temperate regions such as New York State as milder winters fail to kill the disease carrying insects. (The increase in the incidence of West Nile virus may be an example of this.)

Ozone Depletion
CFC’s (chloroflurocarbons) are very active chemicals associated with certain human manufacturing processes and products. This CFC pollution from refrigerants and plastics are destroying our thin ozone shield high up in our atmosphere or in the stratosphere. This layer of ozone normally shields us from excessive incoming ultraviolet radiation. Some consequences of this ever increasing ozone depletion appear to be an increased incidence of skin cancers and cataracts in the human population.

Nuclear Energy
While nuclear energy avoids many of the pollution drawbacks associated with the increased burning of fossil fuels, there are many risks associated with the use of nuclear fuels for energy. Environmental dangers exist in reference to obtaining, using, and storing the wastes from these fuels. Many of the waste products of used nuclear fuel stay in the environment for thousands of years and release radiation which is harmful to humans or other living things. Additionally, the water used to cool many nuclear reactors must be released eventually to the environment. The thermal pollution associated with this released heat into the water is potentially dangerous to the aquatic life in the area where this hot water is released.

Other Factors Influencing Environmental Quality
Many different factors besides industry and resource use have influences on environmental quality. Some factors include population growth and distribution, resource use, the capacity of technology to solve environmental problems, as well as economic, cultural, political, and ethical views.

Some Examples of Political or Cultural Views Influencing Environmental Quality

• Wealthy people in the developed world tend to have fewer children.
• Some countries like China have laws concerning the number of children a couple may have without penalty.
• In some countries such as many in Latin America, families tend to be larger as birth control violates religious and societal norms.
• In some poor cultures in third world countries, having many children is seen as a means of having economic security in old age.

Through a greater awareness of ecological principles and application of these principles to our natural environment, humans can help assure there will be suitable environments for succeeding generations of life on our planet.

Individuals in our societies will always have to make decisions on proposals involving the introduction of new technologies. Individuals in these societies need to make decisions which will assess the risks, benefits, trade-offs, and costs of these new technologies. The economic rewards of these technologies must be properly balanced with any adverse consequences these new technologies may have on the environment. It may be impossible to completely assess the consequences of introducing a new technology, but critical questions in reference to its introduction must be asked.

While the overall impact of humans on the planet’s ecosystems have been negative, humans have done many things to improve the overall quality for living things in ecosystems we have damaged or destroyed. Activities having possible adverse effects on the environment in New York State are subject to review by SEQR (State Environmental Quality Review Act). Some other ways in which humans have attempted to minimize negative impacts or improve the ecosystems we are all a part of are listed in the table which follows.

Some Positive Influences of Humans on the Ecosystem

• Sustaining endangered species by using habitat protection methods such as wildlife refuges and national parks.
• Passing wildlife management laws, such as game laws and catch restrictions.
• Adding lime to Adirondack lakes in an effort to neutralize their acid pollution so the original living things in these lakes can be reintroduced.
• Design new products which meet basic needs without generating pollution.
• Inspection of all materials before entering the country to prevent pest introduction.
• Increased use of biodegradable packaging materials which will recycle themselves quickly to the environment.
• Use fuels which contain less pollutants, such as low sulfur coal and oil.
• Remove pollutants by using such devices as afterburners or catalytic converters before they enter the air.