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Seventh Grade Review Life Science Living organisms require food, water, shelter, energy, and space to survive Cells are the smallest units that carry out activities of life The cell membrane forms the outer boundary of the cell and only allows certain things to enter and exit Cytoplasm is the gel-like material inside the cell The cell wall is located outside of the cell membrane and is used to support and protect the cell found in plants, monerans, and fungi. The nucleus directs all of the activities of the cell and contains all of the genetic blueprints for the operations of the cell The endoplasmic reticulum acts as the highway system of the cell and moves materials around the cell, Golgi bodies of the cell packages materials to be moved to the outside of the cell The mitochondria of a cell are the powerhouse of the cell that breaks down food molecules and produces energy for the cell Lysosomes of a cell digest and destroy waste products and worn-out cell parts. Vacuoles are temporary storage units for the cells that may contain food, water, or waste Ribosomes make proteins for the cell The differences between plant cells and animal cells are: plant cells have chloroplasts, cell walls, and larger vacuoles. Animal cells have centrioles during mitosis • Similarities and differences in plants and animals are evident at the cellular level. Plant and animal cells contain some of the same organelles and some that differ. Chloroplasts are organelles in plant cells that transform light energy into chemical energy in the form of sugar CH O 6 12 6 glucose Cell Theory • The development of cell theory can be attributed to the major discoveries of many notable scientists. The development of cell theory has been dependent upon improvements in the microscope technologies and microscopic techniques throughout the last four centuries. Cell Theory Cell theory includes the following components: all living things are composed of cells; cells are the smallest unit (structure) of living things that can perform the processes (functions) necessary for life; and living cells come only from other living cells. Anton van Leeuwenhoek, in the mid 1600’s, created a simple microscope, and with a tiny glass bead for a lens Robert Hooke, in 1665, looked at slices of cork under his microscope, and called the “empty boxes” he saw cells In 1839, Matthias Schleiden, studied plants and concluded that all plants were made of cells In 1839, Theodor Schwann, studied animals and concluded that all animals were made of cells Rudolph Virchow, in 1856, hypothesized that older cells divide to form new cells The three components of the cell theory are: • 1) all organisms are made up of one of more cells • 2) cells are the basic unit of structure and functions in all organisms • 3) all cells come from cells that already exist Cell Reproduction • Mitosis is the process in which the nucleus of a cell divides and replicates to form two identical nuclei in a series phases: prophase, metaphase, anaphase, and telophase • Meiosis is the process of division in cells that produces sex cells Interphase Interphase is not part of mitosis but is included here as a reminder that interphase preceeds mitosis. Prophase Metaphase Anaphase Telophase Cell Reproduction • The purpose of mitosis is to produce new cells for growth and repair that are identical to the parent cell. The purpose of meiosis is to produce reproductive (sex) cells that carry half the genetic material of the parent Differentiate between the purpose of mitosis and meiosis Cells that have the same goal group together to form tissues, tissues that have the same goal group together to form organs, organs with similar goals group to form organ systems Unicellular organisms are made of only one cell Multi-cellular organisms are made of many cells • Multi-cellular organisms exhibit a hierarchy of cellular organization. They are complex in that there is a division of labor among the levels of this hierarchy for carrying out necessary life processes. Cells perform numerous functions and processes including respiration, waste removal, growth, irritability, and reproduction Cells strive to maintain equilibrium • Osmosis is the passive transport of water molecules across a cell membrane. Diffusion is the passive transport of substances other than water across a cell membrane. Cell membranes are selectively permeable to various substances. Binomial nomenclature is the system used for classifying organisms • Kingdoms are arranged using system of names recognizable around the world Division into Kingdoms is based on: • Information about physical features and activities is arranged in a hierarchy of increasing specificity. The levels in the accepted hierarchy include domain, kingdom, phylum, class, order, family, genus and species. Current classification systems now generally recognize the categorization of organisms into three domains, Archaea, Bacteria and Eukarya. • Any grouping of organisms into domains or kingdoms is based on several factors, including the presence or absence of cellular structures, such as the nucleus, mitochondria, or a cell wall; whether the organisms exist as single cells or are multicellular; and how the organisms get their food. For example, simple, single-celled organisms that are able to survive in extreme environments are believed to be fundamentally different from other organisms and may be classified in their own domain (Archaea). Four different kingdoms of the Eukarya domain of organisms are generally recognized by scientists today (Protista, Fungi, Plants, and Animals). Moneran Kingdom • • • • Unicellular, prokaryotic cells No nucleus All have a cell wall Monerans are classified into two groups, autotrophs, and heterotrophs. • Or bacteria and cyanobacteria • Or Eubacteria or Archaebacteria Protista Kingdom • Unicellular or multicellular, eukaryotic • nucleus • membrane • form colonies or chains • absorbs, ingests or photosynthesize food Fungi Kingdom • Multi-cellular eukaryotic organisms • Parasitic or saprophytic • Reproduce using spores Plants Kingdom • Multi-cellular eukaryotes • Producers, cells contain chlorophyll • Divided into nonvascular and vascular • Four important plant groups are the mosses, ferns, conifers, and flowering plants. Animal Kingdom • Divided into nonvertebrates and vertebrates • Eukaryotic cells • Some important animal groups (phyla) are the cnidarians, mollusks, annelids, arthropods, echinoderms, and chordates. Species • A group of similar-looking organisms that can interbreed under natural conditions and produce offspring that are capable of reproduction defines a species. Producers make their own food by photosynthesis and are the beginning of food chains • Chlorophyll is a chemical in chloroplasts that can absorb or trap energy and transform it into chemical energy called glucose Photosynthesis is the necessary life process that transforms light energy into chemical energy. It involves a series of chemical reactions in which the light energy is used to change raw materials (carbon dioxide and water) into products (sugar and oxygen). The energy is stored in the chemical bonds of the glucose (sugar) molecules. Plants perform cellular respiration as well as photosynthesis. Plants convert the sugars they produce into other raw materials that are used by plants and animals for growth, repair, and energy needs. • Energy is a basic need of all living things. Photosynthesizing organisms obtain their energy from the sun. Plants and other photosynthesizing organisms are often called producers because of their ability to produce glucose (sugar). Photosynthesizing organisms are at the base of the energy pyramid. LS.6 • In order to understand how an ecosystem functions, one must understand the concept of a system and be able to envision models of systems. The four parts of the water cycle are evaporation, condensation, precipitation, and collection (infiltration). In the carbon dioxide oxygen cycle, producers release oxygen for consumers who release carbon dioxide for the producers. Nitrogen cycle is the circular path in which nitrogen moves through the environment. Nitrogen is a gas that makes up 78% of the earth’s atmosphere. Nitrates are a combination of oxygen and nitrogen, absorbed by the roots of plants Nitrifying bacteria converts ammonia from dead plants and animals and animal waste to nitrates that can be used by plants Denitrifying bacteria converts ammonia from dead plants and animals and animal waste. Nitrogen, which is released into the atmosphere Nitrogen converters combine oxygen and nitrogen to make nitrates. Ex. Lighting, bacteria in the soil, algae in wet areas Ammonia is a gas given off by dead plants and animals waste A pyramid shows relative amounts of energy available to each level. Omnivores are animals that eat animals and plants. Herbivores are animals that eat only plants. Carnivores are animals that eat only meat. • The amount of energy available to each successive trophic level (producer, first-order consumer, second-order consumer, thirdorder consumer) decreases. This can be modeled through an energy pyramid, in which the producers provide the broad base that supports the other interactions in the system. • • • 1st level consumer-Primary consumer usually herbivores, animals that eat plants and algae. 2nd level consumers- Secondary consumers usually carnivores, animals that eat the primary producers. 3rd level consumers- Tertiary consumer’s animals that don’t have predators, they are considered the top of the food chain. Food Chain • A food chain is a diagram of relationships between living organisms. Shows living things depend on other things to live. Animals eat other animals to survive. A complex balance of life. If one animal’s source of food disappears, other animals may be impacted and die. A food web is two or more food chains hooked together You are getting there!!!! • Almost as smart as a seventh grader!!!!!