Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)Chapter 1

Lesson 1

Vocabulary

Asexual ReproductionAutotrophCellControlled ExperimentDevelopment

HeterotrophHomeostasisMetabolismMulticellularOrganism

ResponseSexual ReproductionSpontaneous GenerationStimulusUnicellular

Key Concepts

What are the Characteristics of All Living Things? o All organisms, or living things, share six important characteristics. All living things have a

cellular organization, contain similar chemicals, use energy, respond to their surroundings, grow and develop, and reproduce. All organisms are made up of cells. A cell is the basic unit of structure and function in an organism. Single-celled organisms, like bacteria, are unicellular organisms. Organisms composed of many cells are multicellular. The chemicals in cells include water, carbohydrates, proteins, and lipids. Nucleic acids are the genetic material of cells. The combination of reactions that break down and build up materials to provide a cell with energy is metabolism. A change in an organism’s surroundings that causes the organism to react is called a stimulus. An organism reacts to a stimulus with an action or change in behavior called a response. Development is the process of change that occurs during an organism’s life to produce a more complex organism. Asexual reproduction involves only one parent and produces offspring that are identical to the parent. Sexual reproduction involves two parents and combines their genetic material to produce a new organism that differs from both parents.

Where Do Living Things Come From? o Living things arise from other living things through reproduction. The idea that living things

could arise from nonliving things, or spontaneous generation, was proved incorrect by the controlled experiments of Francesco Redi and Louis Pasteur, which were a series of identical tests in which only one factor was a variable.

Why Do Living Things Need to Survive? o Regardless of size, all living things have the same basic needs. All living things must satisfy their

basic needs for food, water, living space, and stable internal conditions. Organisms that make their own food are called autotrophs. Organisms that cannot make their own food are called heterotrophs. Heterotrophs eat autotrophs or other heterotrophs. The maintenance of stable internal conditions is called homeostasis. Homeostasis is essential to proper cell functioning.

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)Lesson 2

Vocabulary

Binomial NomenclatureClassification

GenusSpecies

Taxonomy

Key Concepts

Why Do Biologists Classify Organisms?o To date, scientists have identified more than one million kinds of organisms on Earth – and that

number keeps growing as scientists discover new organisms. To bring order to the astonishing number of living things, scientists group organisms based on similarities, or classify them. Classification is the process of grouping things based on similarities. Biologists use classification to organize living things into groups so that the organisms are easier to study. The scientific study of how living things are classified is called taxonomy. Taxonomy also involves naming organisms. The system scientists use, developed by Swedish botanist Carolus Linnaeus, is called binomial nomenclature. Under it, each organism has a unique two-part scientific name. The first word is the genus, a classification grouping that contains similar, closely related organisms. The second word often describes where an organism lives or its appearance. A species is a group of similar organisms that can mate with each other and produce offspring that can also mate and reproduce.

What Are the Levels of Classification? o Most biologists today use a classification system that has eight levels. A domain is the highest

level of organization. Within a domain, there are kingdoms. Within kingdoms, there are phyla. Within phyla are classes. Within classes are orders. Within orders are families. Each family contains one or more genera. Finally, each genus contains one or more species. The more classification levels two organisms share, the more characteristics they have in common and the more closely related they are.

How Are Taxonomic Keys Useful? o Taxonomic keys are useful tools that help determine the identity of organisms. A taxonomic key

consists of a series of paired statements that describe the various physical characteristics of different organisms. By choosing one statement in each pair and following its directive, the identity of an unfamiliar organism can eventually be determined.

Lesson 3

Vocabulary

Eukaryote Nucleus Prokaryote

Key Concepts

How Are Organisms Classified Into Domains and Kingdoms? o Taxonomy has come a long way since the time of Linnaeus. Since then, microscopes have

helped scientists discover tiny new organisms and identify differences among cells. The modern classification system is made up of three domains. Within the domains are kingdoms. Organisms

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)are placed into domains and kingdoms based on their cell type, their ability to make food, and the number of cells in their bodies. The three domains are Bacteria, Archaea, and Eukarya.

o Bacteria are all around you – on the surfaces you touch and even inside your body. Some are autotrophs, while others are heterotrophs. Members of domain Bacteria are prokaryotes, or organisms whose cells lack a nucleus. A nucleus is a dense area in a cell that contains nucleic acids, which are the chemicals that direct all of the cell’s activities. In prokaryotes, nucleic acids are not contained within a nucleus.

o Like bacteria, members of domain Archaea are also unicellular prokaryotes that can be autotrophs or heterotrophs. Archaea are classified in their own domain because their chemical makeup differs from that of bacteria. Bacteria and archaea also differ in their structure and chemical makeup of their cells. Archaea can be found in extreme environments.

o Domain Eukarya consists of eukaryotes, organisms with cells that contain nuclei. Domain Eukarya is divided into four kingdoms: protists, fungi, plants, and animals. Organisms in these four kingdoms can be unicellular or multicellular. The protist kingdom is sometimes called the “odds and ends” kingdom. It includes any eukaryote that cannot be classified as an animal, plant, or fungus.

o Mushrooms, molds, and mildew are all members of the fungi kingdom. Most fungi feed by absorbing nutrients from dead or decaying organisms. The plant kingdom includes a great variety of organisms, from giant redwood trees to mosses. All plants are autotrophs that make their own food. Members of the animal kingdom are all heterotrophs. Animals have different adaptations that allow them to locate food, capture it, eat it, and digest it.

Lesson 4

Vocabulary

Branching Tree DiagramConvergent Evolution

EvolutionShared Derived Characteristic

Key Concepts

How Are Evolution and Classification Related?

In 1859 Charles Darwin published a theory about how species could change over time. Darwin’s theory is often referred to as the theory of evolution. Evolution is the gradual change in a species over time. Darwin believed that evolution took place through the process of natural selection in which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

The theory of evolution has changed how biologists classify organisms. Scientists now understand that certain organisms may be similar because they share a common ancestor and an evolutionary history. The more similar the two groups are, the more recent the common ancestor probably is. Today’s system of classification takes into account the history of a species. Species with similar evolutionary histories are classified more closely together. Probable evolutionary relationships among groups of organisms and the order in which specific characteristics may have evolved are illustrated using a branching tree diagram. The base of such a diagram shows the common ancestor. Organisms are grouped according to

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)their shared derived characteristics, which are usually homologous structures, or structures that have the same evolutionary origin. In addition to comparing the structures of organisms, scientists can also use information about the chemical makeup of their cells.

Unrelated organisms may have similar characteristics or body structures because they evolved in similar environments. The process by which unrelated organisms evolve characteristics that are similar is called convergent evolution. When studying the chemical makeup of organisms, scientists sometimes discover new information that results in reclassification.

Chapter 2

Lesson 1

Vocabulary

Cell Cell Theory Microscope

Key Concepts

What Are Cells? o Cells are the basic units of structure and function in living things. Cells form the parts of an

organism and carry out all of its functions. Every organism is made out of one or more cells, and each cell can carry out the basic functions that let it live, grow, and reproduce. Those functions can include obtaining food, water, and oxygen, secreting wastes, and reproducing by division.

What Is the Cell Theory? o The cell theory explains the relationship between cells and living things. It was developed about

two hundred years after the invention of the microscope, an instrument that makes small objects look larger, and the discovery of cells. The cell theory states the following:

All living things are composed of cells. Cells are the basic units of structure and function in living things. All cells are produced from other cells.

How Do Microscopes Work? o Most cells are too small to be seen by the human eye, so the development of the cell theory

depended on observations made through microscopes. Some microscopes focus light through lenses to produce a magnified image, and other microscopes use beams of electrons. A compound microscope uses two lenses and focuses light from a lamp or reflected from a mirror. This type of microscope is often used in classrooms. You can estimate the true size of an enlarged object by measuring the width of the circular field visible through the microscope and comparing the size of the object to the width of the field.

o Objects viewed through a microscope are also more detailed than when viewed with the naked eye. Microscopes improve resolution: the ability to distinguish separate structures that are close together. Electron microscopes have better resolution and magnification than light microscopes.

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)

Lesson 2

Vocabulary

Cell wallCell MembraneNucleusOrganelleRibosomeCytoplasm

MitochondriaEndoplasmic ReticulumGolgi apparatusVacuoleChloroplastLysosome

MulticellularUnicellularTissueOrganOrgan System

Key Concepts

How do the parts of a cell work? o Cells contain a number of smaller structures that divide up the jobs inside the cell. Each kind of

cell structure has a different function within a cell. Every cell is surrounded by a cell membrane, which controls the movement of materials into and out of the cell. Jobs inside the cell are handled by specialized organelles suspended in the cell’s gel-like cytoplasm: the nucleus directs the cell’s activities, lysosomes break down food into smaller particles, mitochondria convert the energy stored in food to energy the cell can use, ribosomes produce proteins, and the endoplasmic reticulum and Golgi apparatus modify the proteins and move them around inside the cell. Vacuoles are structures where the cell can store water, food, or wastes. Plant cells have two structures that are not found in animal cells: the cell wall, which surrounds the cell and helps support it, and chloroplasts, which capture the energy in sunlight to power the process the plant uses to make its own food.

How do cells work together in an organism? o In a unicellular organism, all of the functions of life are carried out by one cell. Each cell in a

multicellular organism like a plant or an animal also carries out the same basic functions to remain alive, but they may also be specialized to perform specific functions for the organism as a whole. In multicellular organisms, cells are organized into tissues, organs, and organ systems. A tissue is a group of specialized cells that work together to perform a particular function. An organ contains different tissues that function together, and an organ system is a group of organs that work together to perform a major function.

Lesson 3

Vocabulary

ElementCompoundCarbohydrate

LipidProteinEnzyme

Nucleic AcidDNADouble Helix

Key Concepts

What are elements and compounds? o Living things contain compounds built out of a small set of elements. An element is any

substance that cannot be broken down into simpler substances. The smallest unit of an element is

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)a particle called an atom. Compounds form when two or more elements combine chemically. When elements combine, they form units called molecules.

What compounds do cells need? o Many compounds in living things contain the element carbon. Most compounds containing

carbon are called organic compounds. Some important groups of organic compounds that living things need include carbohydrates, lipids, proteins, and nucleic acids. Water is a necessary inorganic compound. About two-thirds of every living thing is water.

o Carbohydrates (sugars, starches) and lipids (fats, oils, waxes) are energy-rich compounds containing carbon, hydrogen, and oxygen. Carbohydrates are used for energy in living things and are important components in cell walls and on cell membranes. Cells use lipids to store energy for later use, and cell membranes are made of lipid.

o Proteins are large organic molecules containing carbon, hydrogen, oxygen, and nitrogen (and in some proteins, sulfur). Proteins make up parts of the cell membrane and organelles. Specialized proteins called enzymes speed up chemical reactions inside living things.

o Nucleic acids are long molecules containing carbon, hydrogen, oxygen, nitrogen, and phosphorus. They include DNA, the molecule that stores the genetic information used to control the cell. The shape of a DNA molecule is called a double helix.

Lesson 4

Vocabulary

Selectively PermeablePassive TransportDiffusion

OsmosisActive TransportEndocytosis

Exocytosis

Key Concepts

How do Materials Move into and out of cells? o All of the materials that cells need – such as food, water, and oxygen – as well as the wastes that

they must get rid of, move through the cell membrane. Cell membranes are selectively permeable: a double layer of lipid molecules prevents some substances from passing through the membrane but lets other molecules move through. Molecules that cannot freely pass through the membrane must cross through one of the proteins embedded in it. Substances that can move into and out of a cell do so by means of one of two processes: passive transport or active transport.

o Passive transport is the movement of materials through the membrane without the use of cellular energy. There are several forms of passive transport. Small molecules that can freely cross the cell membrane move by diffusion, moving from areas of high concentration to areas of lower concentration. Oxygen and carbon dioxide enter and leave the cell by diffusion. Water also crosses the cell membrane easily, by a passive process called osmosis. Molecules that cannot move through the cell membrane can diffuse through specialize protein cannels in a process called facilitated diffusion.

o Active transport uses cellular energy to move materials through the cell membrane. Some of the proteins in the cell membrane can move small molecules in the opposite direction than diffusion would take them: from an area of lower concentration to a region of higher concentration. These

Science 5/6 – 2nd Trimester Study Guide (Covers All of Chapter 1 and Chapter 2)proteins are called transport proteins. Materials that are too large to pass though transport proteins are also moved by active transport: during endocytosis the cell membrane changes shape to engulf particles, during exocytosis vacuoles fuse with the membrane to expel large particles.