Unit 1.1 Characteristics of Life

Transcription

1 Unit 1.1 Characteristics of Life 1. Life Has Organization As a organism lives it maintains its organization by using different life processes. Living organisms are organized from the simplest to the most complex. Atoms make up molecules. Molecules make up cell organelles. Cell organelles make up cells. Cells make up tissues. Tissues make up organs. Organs make up organ systems, and organ systems make up an organism. The way these are arranged determines the type of organism produced. Unity refers to the many similarities between different living organisms. For example, cats, dogs, pigs and horses all have four legs. These are general similarities. More specifically, all dogs will have many similar characteristics and are considered to be the same species. Diversity refers to there being a great difference among living things. For example, there is a great difference between humans even though we are from the same species. 2. Life Needs To Acquire Energy Living things must acquire nutrients so that they can be used to build and maintain the structures of the organism. Energy is needed to maintain the work done by the organism. 3. Homeostasis The internal environment stays the same despite an ever changing external environment. For example, the body must try and maintain a temperature of 37 degree Celsius despite what the temperature is outside the body. 4. Respond To Stimuli An organism responds to stimuli by moving. These behaviours are done to minimize injury, to reproduce and to gather a food source. All living things interact with the external surroundings. For example, a change in temperature may cause certain animals to migrate. 5. Must Be Able To Reproduce Must be able to pass on the organism's hereditary information. This may be done by asexual reproduction or by sexual reproduction. Asexual reproduction is usually done by unicellular organisms which pass on identical DNA to their offspring. Sexual reproduction is usually done by multicellular organisms which pass on half the genetic information to their offspring. Continuity of life is what organisms strive for even to the point that it will die at the expense to reproduce. 6. Must Be Able To Grow And Develop Organisms increase in size and the number of cells they possess. Human development includes all changes that takes place from birth to death. The parts of an organism and their arrangement are related to the function. For example, we have many bones and joints that can move. This movement allows us to move and manipulate objects. Another example are fish. They have gills that allow them to breathe under water. 7. Adaptations 1

2 These are changes to an organism so that it is best suited to its own environment. Adaptations are selected by evolution. When new variations are within a particular species, certain members of that species may be able to capture more food and survive in higher numbers and have more offspring than the poorly adapted members. All life is not identical to what was once in the past. Organisms change through time. Review Questions: 1. All living things are composed of, the smallest unit of life. 2. All living things need a source of and of to maintain themselves. 3. When a plant bends towards the light, it is to an external stimulus. 4. When living things, the offspring resembles the parents. 5. Living things are suited, that is, to their environment. 6. Living things are in a state of, that is, the internal environment stays relatively constant. Answers: cells, energy and of nutrients, responding, reproduce, adapted, homeostasis Unit 1.2 Ecosystems Definitions: Population all the members of one species. Community a group of populations of all organisms living together. Ecosystem consists of the various interactions among populations and with the environment. Biosphere the surface of the earth where life has the ability to live. Effect of Humans on the ecosystem Human presence has threatened many aspects of the biosphere. Humans change existing ecosystems. The human increase in population threatens the stability and diversity of the planet. It is ironic that this instability threatens the human population itself. For example, the destruction of the rain forest may lead to increase in carbon dioxide, which raises the world temperature. Change in temperature causes many organisms to die. Many of these organisms are needed for humans to survive. It is estimated that there are over 80 million species in the world; of which, only 2 million have been identified. This biodiversity has been altered by humans affecting the 2

3 environment, polluting, developing and over harvesting natural resources. Extinction occurs naturally, but many extinctions happening each day are caused by humans. The extinction of species reduces valuable resources available to humans. Review Questions: 1. A(n) is when populations within a community interact with one another and the environment. 2. All organisms that live in one common area make up a(n). 3. When many populations live together it is called a(n). 4. All living things on earth make up the. 5. When the human population increases in size the ecosystem becomes. 6. Burning fossil fuels produces a mass amount of Carbon Dioxide. The is able to filter the majority of this waste. 7. A(n) is many animals that have similar characteristics and has the capability to produce offspring. 8. When the environment changes and the members of species are unable to adapt to the change, the outcome will most likely lead to. Answers: ecosystem, population, community, biosphere, threatened, tropical rain forest, species, extinction. 1.3 Classification Taxonomy is a branch of biology that names and groups organisms according to their characteristics and evolutionary history. Aristotle ( B.C.) was the first to classify living organisms. This Greek philosopher grouped animals into two categories. The particular organism was classified as either plant or animal origin. As time progressed, modern science and rapid research identified many new organisms. Aristotle s classification was not sufficient. The Swedish naturalist Carolus Linnaeus ( ) realized that such a system was not conducive for modern biology. Linnaeus made two main contributions to taxonomy. Linnaeus developed a classification system of organizing organisms into hierarchal categories. He did this be using the physical appearances of organisms to group them. He was also instrumental in developing the binomial nomenclature. Binomial Nomenclature Biologists give each living thing a binomial or two part name. For example Homo sapiens is the Binomial name for humans. The first word is the Genus and the second is the species. 3

4 These are universal among biologist to avoid confusion. Linnaeus realized that common names caused a problem as they varied from region to region. For example a jelly fish is not a fish, or a sea horse is not a horse. Hierarchal Classification This includes seven different levels of organization. Kingdom, Phyla, Classes, Orders, Families, Genera, and Species are included in the seven. Kingdom being less specific and species becoming more specific. A mnemonic device used to remember this could be: Kings Play Calgary On Friday Gretzky Scores. Kingdom Animalia Animalia Animalia Phylum Chordata Chordata Chordata Class Mammalia Mammalia Mammalia Order Primates Carnivora Perissodactyla Family Hominidae Felidae Equidae Genus Homo Felis Equus species sapiens domesticus caballus Humans House cat Horse For many years, most biologists favored a Five-Kingdom system consisting of Kingdoms Monera, Protista, Fungi, Plantae, and Animalia. They were placed into categories by their type of cell (prokaryotic or eukaryotic), level of organization (unicellular or multicellular), and how they acquire their nutrition. It is suggested that protests evolved from the Monerans who are the simplest organism. Fungus, Plants and Animals evolved from the Protists in three separate evolutionary lines. The five kingdom system of classification is based on structural differences and also on modes of nutrition among the eukaryotes. 4

5 A New Proposal: The Three Domains of Life In the 1970 s scientists began to find evidence for a previously unknown group of prokaryotic organisms. These organisms lived in extreme environments such as the Dead Sea, acid lakes, and salt evaporation ponds. These are environments that scientists never suspected of maintaining any life. Because they appeared prokaryotic, they were considered bacteria and named "archaebacteria" ('ancient' bacteria). However, it became obvious from biochemical characteristics and DNA sequence analysis that there were numerous differences between these archaebacteria and other bacteria. Before long, it was realized that these archaebacteria were more closely related to the eukaryotes than to bacteria. Today, these bacteria have been renamed Archaea. From this work scientists proposed that there should be a new category of classification of life, called the Domain. The Domain is a classification category above Kingdom. The traditional 5 Kingdom system says nothing about how organisms within Kingdoms or between kingdoms may be related to each other via evolutionary relationships among the kingdoms. A New Proposal is the Three Domains of Life. The three domains are Bacteria, Archaea, and Eukarya. The three-domain system of classification is based on biochemical differences that show they are three vastly different groups of organisms. See table 27.3 on page 561 titled Classification Criteria for the Three Domains. Viruses are not in ANY of these kingdoms, scientists do not classify them as 'alive'. 5

6 Taxonomy 1. Why Classify? Scientists have identified more than 2.5 million kinds of organisms. Some biologists estimate that there may be another 20 million unknown species still out there (insects in tropical rain forests, creatures living in the unexplored depths of the sea, and microorganisms living all around us). The only way to study this great diversity of organisms is to divide living things into groups. 2. Biological Classification: 18 th century, an organism s name was based on Latin or ancient Greek words because these languages were understood by scientists everywhere. Carolus Linnaeus, a Swedish botanist, developed a system known as binomial nomenclature: each organism has a two-part scientific name. Ex: Acer rubrum (red maple) Acer is the genus name. rubrum is the species name. Genus name: refers to the relatively small group of organisms to which a particular type of organism belongs (all maple trees are in the genus acer). Species name: usually a Latin description of some important characteristic of the organism (rubrum is the Latin word for red). Two Important Naming Conventions to remember: 1) Always capitalize the Genus name but not the species name. 2) When typing, always italicize the entire name (Genus and species). E.g. Homo sapiens 3) When hand-writing, it is difficult to italicize, so instead, underline the name. E.g. Homo sapiens The groups to which organisms are assigned are called taxa (singular: taxon) and the science of naming organisms and assigning them to these groups is called taxonomy. There are 7 taxa in total, these are (from largest to smallest): Kingdom Phylum Class Order Family Genus Species King Philip Came Over For Good Scotch The Five Kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. 6

7 1.4 The Scientific Method The Process of Science Science observes and looks at the natural world. These observations and conclusions are subject to change if new information arises from new investigations. When many people get the same conclusions and findings over and over again their concept then becomes a theory. One can never say that a theory is correct. They can only say that the theory is supported by data and evidence. The Scientific Method 1. Make an observation. New observations are made and previous data are studied. 2. Formulate a hypothesis (a possible explanation of the observation) Must be in an if then statement. A valid hypothesis must be able to do three things: a. It must be able to explain the observations that led to its development. b. It must be able to predict new findings. c. It must be testable. Experiment to be done Prediction If Something is done to the test group (experiment to be done), then something should happen (prediction) Example Question #1: Does changing temperature result in a change in bacteria growth? Hypothesis: If the temperature of a bacterial culture is raised by 5 C THEN the bacteria will grow faster. Example Question #2: Will lack of oxygen affect plant growth? Hypothesis: If plants are deprived of oxygen, then they will show no less growth. 3. Test the hypothesis. Must be controlled and repeatable. One must accumulate data. Data A collection of facts related to a particular question (hypothesis) Fact - Something that all observers would agree is true 4. Formulate a conclusion 5. Report your findings. Valid Experiment In order to be valid, experiments must be: 1) Repeatable: Others wishing to test the hypothesis must be able to duplicate the experiment The experiment must be able to make the same observations and collect similar Data. 2) Controlled: The experiment must be conducted systematically so it is clear what factors caused the results. The control is not subjected to the experimental variable. The experimental variable is the element being tested. Only one factor is tested at a time. The dependable variable is the result of the change 7

8 Review Questions: 1. A concept that is based on observations and conclusions from past experiments are called. 2. For scientists to do research and gather information they should follow what type of approach?. 3. Can a hypotheses be proven true? 4. Are hypotheses falsifiable? 5. Generalizing from facts is inductive reasoning, but when scientist decide what further observations and experiments are needed, it is called. 6. Steps involved in the scientific method include making an observation, formulating (a), (b), and coming to a (c). 7. Results of an experiment must be since other scientist must get the same results. 8. The goes through all steps of an experiment except the one being tested. 9. The variable is the one being tested. Answers: theories, scientific method, no, yes, deductive reasoning, hypothesis, testing, conclusion, repeatable, control, experimental. 1.5 Using a Dichotomous Key (You will need to know this for the Unit 1 Quiz) Dichotomous di chot o mous : dividing into two parts (Late Latin dichotomos, from Greek, from dich- + temnein to cut) Scientists often use a dichotomous key to identify species they have observed. This type of key is easy to use, and is much like a choose your own ending novel, except that choices given usually consists of the presence or absence of a structure. Start with the first pair of characteristics, and decide which of the two statements are true. Follow the next number given until you reach the name of the organism at the end of the key. On the next page is a very brief example to give you the idea: 8

9 Organism X has scales, is aquatic, four legs, and has a shell. 1. a) has scales Go to 2 b) no scales Go to 5 2. a) aquatic Go to 3 b) not aquatic.go to 3 3. a) has legs..go to 4 b) no legs Order Squamata 4. a) has a shell.order Testudines b) no shell Order Crocodylia ANSWER: Creature X is Order Testudines For practice, use the following key to identify each member of the Smallium genus (pictured on next page): 1. a) Four toes present Smallium ridiculum b) Not four toes...go to 2 2. a) Eyebrows present.go to 3 b) No eyebrows Go to 4 3. a) Eyebrows round or curved Smallium bashfum b) Eyebrows not round, but straight Smallium uglum 4. a) Hair or eyelashes present Go to 5 b) No hair or eyelashes Smallium vulgaris 5. a) Dark eyes Go to 6 b) Not dark eyes Go to 7 6. a) Hair points upward Smallium elegantum b) Hair points downward.. Smallium cuticum 7. a) Eyelashes top and bottom Smallium fantasticum b) Eyelashes top only Smallium splendicum 9

10 a) S. elegantum b) S. splendicum c) S. cuticum d) S. fantsticum e) S. uglum f) S. ridiculum g) S. bashfum h) S. vulgaris Answer Key: 10