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Transcript
Cells The Building Blocks of Life How Did the Earth Form? • We do not know for certain how the Earth formed. • Most scientists agree that the Earth formed about 4.6 billion years ago. • That is 4,600,000,000 years ago. Two Theories of How Life on Earth Formed • Stanley Miller’s Theory of Life • The Volcanic Theory of Life Stanley Miller’s Theory of Life • This theory states that a mixture of gases and water was struck by lightning and formed a “tar-like” substance that allowed living things to develop. • Also known as “Primordial Soup” The Volcanic Theory of Life • The Volcanic Theory of Life states that the cooling planet had lots of volcanoes putting gases into the air. • These gases condensed into rain that formed oceans. • Single cell organisms evolved into plant life then animal life. How did Cells Form? • Several Theories of How Cells Formed: – Cells arose in shallow pools containing “soup” of chemicals. These chemicals become combined and formed cells. – Cells formed in beds of clay that allowed substances (chemicals) to be contained and produce living things – cells. – Meteors and asteroids carried water, containing life (cells) to the Earth. Which Cell Theory Is True? • We still do not know for sure how cells formed. Spontaneous Generation? • The Theory of Spontaneous Generation states that life could arise from non-living matter. – This theory was disproved in 1668 by Francesco Redi who used raw meat for his experiments. Francesco Redi Redi’s Experiment Producers and Consumers • A producer is any organism that makes it’s own food. – Example: green plants • A consumer is any organism that can not produce it’s own food. – Consumers are dependent on other organisms to survive. – Example: Man How Do Producers Make Food? • Photosynthesis: the process by which green plants convert sunlight into food. – As a waste product, oxygen is released. – At some point in history, early cells evolved and became able to perform photosynthesis. • This is important because this allowed an oxygen atmosphere to form and eventually allows for animal life to evolve. Characteristics of Living Things • All living things share characteristics, they: – Are made of cells – Are able to move – Perform complex chemical activities – Are able to grow and develop – Are able to respond to their environment – Are able to reproduce What is a Cell? • The cell is the basic building block of all living things. – The first cells on Earth are thought to have evolved ~3.5 billion years ago. – These cells could not produce their own food. All living things are made of cells Plant Cells Animal Cells All living things are able to move All living things perform complex chemical activities “building up and breaking down” • Metabolism is the sum total of all the chemical reactions that occur in a living thing. – In humans these chemical reactions are ingestion, digestion, respiration, and excretion. Nutrition • Nutrition is the process of obtaining food and breaking it down into a useable form for cell absorption. Ingestion • Ingestion is taking in food to process. Digestion • Digestion is the process of breaking down food into simpler substances. Transport • Nutrients and other necessary materials are delivered to all the cells of the organism; wastes are carried away. Respiration • Respiration is the process of taking in oxygen and using it to produce energy. Excretion • Excretion is the process of getting rid of waste material. Regulation • Regulation is the control and coordination of all life functions. It also involves the response of an organism to changes in the environment. All living things are able to grow and develop • Life span is the maximum length of time that an organism is expected to live. All living things are able to respond to their environment • A stimulus is something that comes from outside the organism or from within the organism that triggers a reaction. Examples: cold breeze stomach growl • A response is the reaction that occurs as a result of the stimulus. Examples: goose bumps eat food All living things are able to reproduce “Like produces like” • Sexual reproduction: – Requires two parents – Results in offspring that show variations • Asexual reproduction: – Requires one parent – Results in identical offspring with no variations Both forms of reproduction give a chemical “blueprint” to the next generation. Cellular Reproduction Egg and Sperm Cells Fertilization Meiosis - Sexual Reproduction Result is daughter cells with half the chromosomes Mitosis – Asexual Reproduction Result is two identical cells What are the Needs of Living Things? • In order to survive all living things need: – Energy – Food – Water – Oxygen – Living space – To maintain a proper temperature How Do Living Things Maintain Proper Temperature • Homeostasis is the ability of an organism to keep the conditions inside the body the same even though external environmental conditions change. • Warm blooded animals maintain a constant body temperature at all times. – Examples are man and mammals • Cold blooded animals have body temperatures that change with the environment. – Examples are fish and reptiles What Makes Up All Living Things? “The Chemistry Of Life” • All living things are made of elements and compounds. What is an Element? • An element is a pure substance that can not be broken down into any simpler substances. – Only 90 natural elements exist on earth. – Only 11 elements are common in living things. – 4 elements (carbon, nitrogen, oxygen and hydrogen) make up 96% of the weight of the human body. What is a Compound? • A compound is formed when 2 or more elements join together chemically. – Examples are: water H2O, and sugar C6H12O6 A water molecule is an example of a compound Cell Theory • The current cell theory states that: – All living things are made of cells. – Cells are the basic unit of structure and function in living things. – Living cells only come from other living cells. What Are Cells Made Of? • Organelles, or “tiny organs”, are the structures that make up a cell. • Organelles were discovered by Robert Hooke in 1665 while looking at cork cells. How Do Cells Function? • Each of the organelles in a cell has a defined function. • There are many organelles that make up a cell. – These include the cell wall, cell membrane, nucleus, cytoplasm, endoplasmic reticulum, ribosomes, lysosomes, mitochondria, vacuoles, chloroplasts. • All organelles working together create the cells structure. Plant Cells vs Animal Cells Plant Cell Animal Cell Cell Organelles – Cell Wall • The cell wall provides support and protection for the cell. • The cell wall is rigid. • Cell walls are only found in plant cells. Cell Wall – only in plants Cell Organelles – Cell Membrane • The cell membrane is the “doorway” of the cell. • Cell membranes control the movement of materials into and out of the cell. – Pores are the openings in the cell membrane. • Cell membranes provide support and protection. – In plant cells the cell membrane is found just inside the cell wall. – In animal cells the cell membrane is the outermost organelle. Cell Membrane Cell Organelles - Nucleus • The nucleus is the “control center”, or “brain” of the cell which controls all activities in the cell. • The nucleus has three parts: – Nuclear membrane – Chromosomes – Nucleolus Cell Organelles - Nucleus • The nuclear membrane controls the movement of materials into and out of the nucleus. • The chromosomes direct the activities within the cell and also pass on genetic traits to the next generation. • The nucleolus, or “little nucleus” is the site of ribosome production. Cell Organelles Cytoplasm • Cytoplasm is the clear, thick jellylike substance that contains all the organelles. Cell Organelles – Endoplasmic Reticulum • The endoplasmic reticulum, or ER, is the tubular transportation system throughout the cell. Endoplasmic Reticulum Smooth and Rough Cell Organelles - Ribosomes • Ribosomes are the protein factories of the cell. • Most ribosomes are found attached to the outside of the endoplasmic reticulum. – This location helps the cell with efficiency of production and transport. Ribosomes Cell Organelles - Lysosomes • Lysosomes are the “clean up crew” of the cell. • Lysosomes are involved in the digestive process of the cell. – Enzymes break down large food into smaller bits for the mitochondria to use. – Lysosomes are not common in plant cells. Cell Organelles - Mitochondria • Mitochondria are the “powerhouse” of the cell and supply most of the energy for the cell. Cell Organelles - Vacuoles • Vacuoles are the “storage tanks” of the cell. • Vacuoles can store food, water, or waste. – In plant cells vacuoles are common. • Usually one large vacuole per cell. – In animal cells vacuoles are not common. • Usually several small vacuoles per cell. Cell Organelles - Chloroplasts • Chloroplasts are the “energy producers” of plant cells. • Chloroplasts are only found in plant cells. • Chloroplasts contain green chlorophyll that captures energy from the sun. How Do Materials Move Into and Out Of The Cell? • Materials enter and leave a cell by one of three methods: – Diffusion – Osmosis – Active Transport What is Diffusion? • Diffusion is the process by which molecules of a substance move from areas of high concentration to areas of low concentration. – The cell membrane is selectively permeable. Diffusion from high concentration to low concentration What is Osmosis? • Osmosis is the diffusion of water into or out of a cell. • Both diffusion and osmosis do not require the cell to use up it’s energy. What is Active Transport? • Active transport is the process by which the cell “carries” a substance in or out. • This requires the cell to use its energy. • When does active transport occur? – If the cell membrane is not permeable for the substance. – If the concentration levels inside and outside the cell are not different enough. What Is Cell Specialization? • In multicellular organisms, cells not only complete its own life activities, but also performs a function that contributes to the life of the organism. • Within multicellular organisms there is division of labor or specialization. – The work of keeping the organism alive is divided up among different parts of the organism. Levels of Specialization Cells combine to form Tissues combine to form Organs combine to form Organ systems combine to form Organism More Specialization Students combine to form Classes combine to form Grades combine to form Schools combine to form District Taxonomy • Taxonomy is the science of naming, describing and classifying organisms. – Living organisms are organized into categories based on characteristics. – The classification system of living organisms is arranged from a large category of kingdom to smaller specific category of species 5 Kingdoms • Monera: one-celled, no nucleus • Protist: one-celled with nucleus • Fungus: many-celled, heterotrophic, lacks chlorophyll • Plant: many-celled, autotrophic, contains chlorophyll • Animal: many-celled, heterotrophic What is a Virus? • A virus is different form other living organisms because it lacks cellular organization. Herpes simplex virus