Cells are organized for more effective functioning in multicellular organisms. Levels of organization for structure and function of a multicellular organism include cells, tissues, organs, and organ systems.
Most cells have cell membranes, genetic material, and cytoplasm. Some cells have a cell wall and/or chloroplasts. Many cells have a nucleus.
Living things are classified by shared characteristics on the cellular and organism level. In classifying organisms, biologists consider details of internal and external struc- tures. Biological classification systems are arranged from general (kingdom) to specific (species).
Each system is composed of organs and tissues which perform specific functions and interact with each other, e.g., digestion, gas exchange, excretion, circulation, loco- motion, control, coordination, reproduction, and protection from disease.
In multicellular organisms, cell division is responsible for growth, maintenance, and repair. In some one-celled organisms, cell division is a method of asexual reproduction.
The nervous and endocrine systems interact to control and coordinate the body’s responses to changes in the environment, and to regulate growth, development, and reproduction. Hormones are chemicals produced by the endocrine system; hormones regulate many body functions.
The processes of sexual reproduction and mutation have given rise to a variety of traits within a species.
Human activities such as selective breeding and advances in genetic engineering may affect the variations of species.
Patterns of development vary among plants. In seed-bearing plants, seeds contain stored food for early development. Their later development into adulthood is character- ized by varying patterns of growth from species to species.
Some organisms are single cells; others, including humans, are multicellular.
The probability of traits being expressed can be determined using models of genetic inheritance. Some models of prediction are pedigree charts and Punnett squares.
Describe simple mechanisms related to the inheritance of some physical traits in offspring.
The male sex cell is the sperm. The female sex cell is the egg. The fertilization of an egg by a sperm results in a fertilized egg.
Multicellular organisms exhibit complex changes in development, which begin after fertilization. The fertilized egg undergoes numerous cellular divisions that will result in a multicellular organism, with each cell having identical genetic information.
Animals and plants have a great variety of body plans and internal structures that contribute to their ability to maintain a balanced condition.
The digestive system consists of organs that are responsible for the mechanical and chemical breakdown of food. The breakdown process results in molecules that can be absorbed and transported to cells.
In all environments, organisms interact with one another in many ways. Relationships among organisms may be competitive, harmful, or beneficial. Some species have adapted to be dependent upon each other with the result that neither could survive without the other.
Herbivores obtain energy from plants. Carnivores obtain energy from animals. Omnivores obtain energy from both plants and animals. Decomposers, such as bacteria and fungi, obtain energy by consuming wastes and/or dead organisms.
A population consists of all individuals of a species that are found together at a given place and time. Populations living in one place form a community. The commu- nity and the physical factors with which it interacts compose an ecosystem.
Given adequate resources and no disease or predators, populations (including humans) increase. Lack of resources, habitat destruction, and other factors such as pre- dation and climate limit the growth of certain populations in the ecosystem.
Since the Industrial Revolution, human activities have resulted in major pollution of air, water, and soil. Pollution has cumulative ecological effects such as acid rain, global warming, or ozone depletion. The survival of living things on our planet depends on the conservation and protection of Earth’s resources.
The latitude/longitude coordinate system and our system of time are based on celestial observations.
The apparent motions of the Sun, Moon, planets, and stars across the sky can be explained by Earth’s rotation and revolution. Earth’s rotation causes the length of one day to be approximately 24 hours. This rotation also causes the Sun and Moon to appear to rise along the eastern horizon and to set along the western horizon. Earth’s revolution around the Sun defines the length of the year as 365 1/4 days.
Most objects in the solar system have a regular and predictable motion. These motions explain such phenomena as a day, a year, phases of the Moon, eclipses, tides, meteor showers, and comets.
The majority of the lithosphere is covered by a relatively thin layer of water called the hydrosphere.
Continents fitting together like puzzle parts and fossil correlations provided initial evidence that continents were once together.
During a physical change a substance keeps its chemical composition and proper- ties. Examples of physical changes include freezing, melting, condensation, boiling, evaporation, tearing, and crushing.
The periodic table is one useful model for classifying elements. The periodic table can be used to predict properties of elements (metals, nonmetals, noble gases).
Vibrations in materials set up wave-like disturbances that spread away from the source. Sound waves are an example. Vibrational waves move at different speeds in different materials. Sound cannot travel in a vacuum.
Most activities in everyday life involve one form of energy being transformed into another. For example, the chemical energy in gasoline is transformed into mechanical energy in an automobile engine. Energy, in the form of heat, is almost always one of the products of energy transformations.
Heat can be transferred through matter by the collisions of atoms and/or mole- cules (conduction) or through space (radiation). In a liquid or gas, currents will facilitate the transfer of heat (convection).
Fossil fuels contain stored solar energy and are considered nonrenewable resources. They are a major source of energy in the United States. Solar energy, wind, moving water, and biomass are some examples of renewable energy resources.
Without direct contact, a magnet attracts certain materials and either attracts or repels other magnets. The attractive force of a magnet is greatest at its poles.
Rocks are composed of minerals. Only a few rock-forming minerals make up most of the rocks of Earth. Minerals are identified on the basis of physical properties such as streak, hardness, and reaction to acid.
The process of weathering breaks down rocks to form sediment. Soil consists of sediment, organic material, water, and air.
The motion of particles helps to explain the phases (states) of matter as well as changes from one phase to another. The phase in which matter exists depends on the attractive forces among its particles.
There are more than 100 elements. Elements combine in a multitude of ways to produce compounds that account for all living and nonliving substances. Few elements are found in their pure form.
Light passes through some materials, sometimes refracting in the process. Materials absorb and reflect light, and may transmit light. To see an object, light from that object, emitted by or reflected from it, must enter the eye.
An object’s motion is the result of the combined effect of all forces acting on the object. A moving object that is not subjected to a force will continue to move at a con- stant speed in a straight line. An object at rest will remain at rest.
Machines can change the direction or amount of force, or the distance or speed of force required to do work.
use and interpret graphs and data tables
differentiate among observations, inferences, predictions, and explanations
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