Some animals and plants are alike in the way they look and in the things they do, and others are very different from one another.
For Grades: 3-5
Learning Goal 1
A great variety of kinds of living things can be sorted into groups in many ways using various features to decide which things belong to which group.
Learning Goal 3
There are millions of different kinds of individual organisms that inhabit the earth at any one time—some very similar to each other, some very different.
For Grades: 6-8
Learning Goal 1
One of the most general distinctions among organisms is between plants, which use sunlight to make their own food, and animals, which consume energy-rich foods. Some kinds of organisms, many of them microscopic, cannot be neatly classified as either plants or animals.
Learning Goal 2
Animals and plants have a great variety of body plans and internal structures that contribute to their being able to make or find food and reproduce.
Learning Goal 3a
Similarities among organisms are found in internal anatomical features, which can be used to infer the degree of relatedness among organisms.
Learning Goal 3b
In classifying organisms, scientists consider details of both internal and external structures.
Learning Goal 4
Traditionally, a species has been defined as all organisms that can mate with one another to produce fertile offspring.
Learning Goal 5
The cycles continue indefinitely because organisms are decomposed after death to return food materials to the environment.
For Grades: 9-12
Learning Goal 1a
The variation of organisms within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions.
Learning Goal 1b
A great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.
Learning Goal 2
The degree of relatedness between organisms or species can be estimated from the similarity of their DNA sequences, which often closely match their classification based on anatomical similarities.
Learning Goal 3
Similar patterns of development and internal anatomy suggest relatedness among organisms.
Learning Goal 4
Most complex molecules of living organisms are built up from smaller molecules. The various kinds of small molecules are much the same in all life forms, but the specific sequences of components that make up the very complex molecules are characteristic of a given species.
Learning Goal 5
A classification system is a framework created by scientists for describing the vast diversity of organisms, indicating the degree of relatedness between organisms, and framing research questions.
Subchapter B
Heredity
For Grades: K-2
Learning Goal 1
There is variation among individuals of one kind within a population.
Learning Goal 2
Offspring are very much, but not exactly, like their parents and like one another.
For Grades: 3-5
Learning Goal 1
Some likenesses between children and parents are inherited. Other likenesses are learned.
Learning Goal 2
For offspring to resemble their parents, there must be a reliable way to transfer information from one generation to the next.
For Grades: 6-8
Learning Goal 1a
In some kinds of organisms, all the genes come from a single parent.
Learning Goal 1b
In organisms that have two sexes, typically half of the genes come from each parent.
Learning Goal 2a
In sexual reproduction, a single specialized cell from a female merges with a specialized cell from a male.
Learning Goal 2b
The fertilized egg cell, carrying genetic information from each parent, multiplies to form the complete organism.
Learning Goal 2c
The same genetic information is copied in each cell of the new organism.
Learning Goal 3
New varieties of cultivated plants and domestic animals have resulted from selective breeding for particular traits.
For Grades: 9-12
Learning Goal 1
Some new gene combinations make little difference, some can produce organisms with new and perhaps enhanced capabilities, and some can be deleterious.
Learning Goal 2
The sorting and recombination of genes in sexual reproduction results in a great variety of possible gene combinations in the offspring of any two parents.
Learning Goal 3
The information passed from parents to offspring is coded in DNA molecules, long chains linking just four kinds of smaller molecules, whose precise sequence encodes genetic information.
Learning Goal 4
Genes are segments of DNA molecules. Inserting, deleting, or substituting segments of DNA molecules can alter genes. An altered gene may be passed on to every cell that develops from it. The resulting features may help, harm, or have little or no effect on the offspring's success in its environment.
Learning Goal 5
Gene mutations can be caused by such things as radiation and chemicals. When they occur in sex cells, they can be passed on to offspring; if they occur in other cells, they can be passed on to descendant cells only. The experiences an organism has during its lifetime can affect its offspring only if the genes in its own sex cells are changed by the experience.
Learning Goal 6a
The many body cells in an individual can be very different from one another, even though they are all descended from a single cell and thus have essentially identical genetic instructions.
Learning Goal 6b
Different parts of the genetic instructions are used in different types of cells, influenced by the cell's environment and past history.
Learning Goal 7
Heritable characteristics can include details of biochemistry and anatomical features that are ultimately produced in the development of the organism. By biochemical or anatomical means, heritable characteristics may also influence behavior.
Subchapter C
Cells
For Grades: K-2
Learning Goal 1
Magnifiers help people see things they could not see without them.
Learning Goal 2
Most living things need water, food, and air.
For Grades: 3-5
Learning Goal 1
Some living things consist of a single cell. Like familiar organisms, they need food, water, and air; a way to dispose of waste; and an environment they can live in.
Learning Goal 2a
Microscopes make it possible to see that living things are made mostly of cells.
Learning Goal 2bc
Some organisms are made of a collection of similar cells that benefit from cooperating. Some organisms' cells vary greatly in appearance and perform very different roles in the organism.
For Grades: 6-8
Learning Goal 1a
All living things are composed of cells, from just one to many millions, whose details usually are visible only through a microscope.
Learning Goal 1b
Different body tissues and organs are made up of different kinds of cells.
Learning Goal 1c
The cells in similar tissues and organs in other animals are similar to those in human beings but differ somewhat from cells found in plants.
Learning Goal 2a
Cells repeatedly divide to make more cells for growth and repair.
Learning Goal 2b
Various organs and tissues function to serve the needs of all cells for food, air, and waste removal.
Learning Goal 3a
Within cells, many of the basic functions of organisms—such as extracting energy from food and getting rid of waste—are carried out.
Learning Goal 3b
The way in which cells function is similar in all living organisms.
Learning Goal 4
About two thirds of the weight of cells is accounted for by water, which gives cells many of their properties.
For Grades: 9-12
Learning Goal 1a
Every cell is covered by a membrane that controls what can enter and leave the cell.
Learning Goal 1b
In all but quite primitive cells, a complex network of proteins provides organization and shape and, for animal cells, movement.
Learning Goal 2a
Within the cells are specialized parts for the transport of materials, energy capture and release, protein building, waste disposal, passing information, and even movement.
Learning Goal 2b
In addition to the basic cellular functions common to all cells, most cells in multicellular organisms perform some special functions that others do not.
Learning Goal 3
The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. Protein molecules are long, usually folded chains made from 20 different kinds of amino acid molecules. The function of each protein molecule depends on its specific sequence of amino acids and its shape. The shape of the chain is a consequence of attractions between its parts.
Learning Goal 4a
The genetic information encoded in DNA molecules provides instructions for assembling protein molecules.
Learning Goal 4b
The genetic information encoded in DNA molecules is virtually the same for all life forms.
Learning Goal 4c
Before a cell divides, the instructions are duplicated so that each of the two new cells gets all the necessary information for carrying on.
Learning Goal 5
Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division. Cell behavior can also be affected by molecules from other parts of the organism or even other organisms.
Learning Goal 6
Gene mutation in a cell can result in uncontrolled division called cancer. Exposure of cells to certain chemicals and radiation increases mutations and thus the chance of cancer.
Learning Goal 7
Most cells function best within a narrow range of temperature and acidity. At very low temperatures, reaction rates are too slow. High temperatures and/or extremes of acidity can irreversibly change the structure of most protein molecules. Even small changes in acidity can alter the molecules and how they interact.
Learning Goal 8
A living cell is composed of a small number of chemical elements mainly carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur. Carbon, because of its small size and four available bonding electrons, can join to other carbon atoms in chains and rings to form large and complex molecules.
Learning Goal 9
Some protein molecules assist in replicating genetic information, repairing cell structures, helping other molecules get in or out of the cell, and generally catalyzing and regulating molecular interactions.
Subchapter D
Interdependence of Life
For Grades: K-2
Learning Goal 1
Animals eat plants or other animals for food and may also use plants (or even other animals) for shelter and nesting.
Learning Goal 2
Living things are found almost everywhere in the world. There are somewhat different kinds in different places.
For Grades: 3-5
Learning Goal 1
For any particular environment, some kinds of plants and animals thrive, some do not live as well, and some do not survive at all.
Learning Goal 2
Insects and various other organisms depend on dead plant and animal material for food.
Learning Goal 3a
Organisms interact with one another in various ways besides providing food.
Learning Goal 3b
Many plants depend on animals for carrying their pollen to other plants or for dispersing their seeds.
Learning Goal 4
Changes in an organism's habitat are sometimes beneficial to it and sometimes harmful.
Learning Goal 5
Most microorganisms do not cause disease, and many are beneficial.
For Grades: 6-8
Learning Goal 1a
In all environments, organisms with similar needs may compete with one another for limited resources, including food, space, water, air, and shelter.
Learning Goal 1b
The world contains a wide diversity of physical conditions, which creates a wide variety of environments: freshwater, marine, forest, desert, grassland, mountain, and others. In any particular environment, the growth and survival of organisms depend on the physical conditions.
Learning Goal 2
Interactions between organisms may be for nourishment, reproduction, or protection and may benefit one of the organisms or both of them. Some species have become so dependent on each other that neither could survive without the other.
Learning Goal 2b
One organism may scavenge or decompose another.
Learning Goal 3
Given adequate resources and an absence of disease or predators, populations of organisms in ecosystems increase at rapid rates. Finite resources and other factors limit their growth.
Learning Goal 4
All organisms, both land-based and aquatic, are interconnected by their need for food. This network of interconnections is referred to as a food web. The entire earth can be considered a single global food web, and food webs can also be described for a particular environment. At the base of any food web are organisms that make their own food, followed by the animals that eat them, then the animals that eat those animals, and so forth.
For Grades: 9-12
Learning Goal 1
Ecosystems can be reasonably stable over hundreds or thousands of years. As any population grows, its size is limited by one or more environmental factors: availability of food, availability of nesting sites, or number of predators.
Learning Goal 2
If a disturbance such as flood, fire, or the addition or loss of species occurs, the affected ecosystem may return to a system similar to the original one, or it may take a new direction, leading to a very different type of ecosystem. Changes in climate can produce very large changes in ecosystems.
Learning Goal 3
Human beings are part of the earth's ecosystems. Human activities can, deliberately or inadvertently, alter the equilibrium in ecosystems.
Subchapter E
Flow of Matter and Energy
For Grades: K-2
Learning Goal 1
Plants and animals both need to take in water, and animals need to take in food. In addition, plants need light
Learning Goal 2
Many materials can be recycled and used again, sometimes in different forms.
For Grades: 3-5
Learning Goal 1
Almost all kinds of animals' food can be traced back to plants.
Learning Goal 2
Some source of "fuel" is needed for all organisms to stay alive and grow.
Learning Goal 3
Over the whole earth, organisms are growing, dying, decaying, and new organisms are being produced by the old ones.
For Grades: 6-8
Learning Goal 1a
Food provides molecules that serve as fuel and building material for all organisms.
Learning Goal 1b
Plants use the energy from light to make sugars from carbon dioxide and water.
Learning Goal 1c
Plants can use the food they make immediately or store it for later use.
Learning Goal 1de
Organisms that eat plants break down the plant structures to produce the materials and energy they need to survive. Then they are consumed by other organisms.
Learning Goal 2
Over a long time, matter is transferred from one organism to another repeatedly and between organisms and their physical environment. As in all material systems, the total amount of matter remains constant, even though its form and location change.
Learning Goal 3a
Energy can change from one form to another in living things.
Learning Goal 3b
Organisms get energy from oxidizing their food, releasing some of its energy as thermal energy.
Learning Goal 3c
Almost all food energy comes originally from sunlight.
For Grades: 9-12
Learning Goal 1
At times, environmental conditions are such that land and marine organisms reproduce and grow faster than they die and decompose to simple carbon containing molecules that are returned to the environment. Over time, layers of energy-rich organic material inside the earth have been chemically changed into great coal beds and oil pools.
Learning Goal 3
The chemical elements that make up the molecules of living things pass through food webs and are combined and recombined in different ways. At each link in a food web, some energy is stored in newly made structures but much is dissipated into the environment. Continual input of energy from sunlight keeps the process going.
Subchapter F
Evolution of Life
For Grades: K-2
Learning Goal 1
Different plants and animals have external features that help them thrive in different kinds of places.
Learning Goal 2
Some kinds of organisms that once lived on Earth have completely disappeared, although they were something like others that are alive today.
For Grades: 3-5
Learning Goal 1
Individuals of the same kind differ in their characteristics, and sometimes the differences give individuals an advantage in surviving and reproducing.
Learning Goal 2
Fossils can be compared to one another and to living organisms according to their similarities and differences. Some organisms that lived long ago are similar to existing organisms, but some are quite different.
For Grades: 6-8
Learning Goal 1
Small differences between parents and offspring can accumulate (through selective breeding) in successive generations so that descendants are very different from their ancestors.
Learning Goal 2a
Individual organisms with certain traits are more likely than others to survive and have offspring.
Learning Goal 2b
Changes in environmental conditions can affect the survival of individual organisms and entire species.
Learning Goal 3a
Many thousands of layers of sedimentary rock provide evidence for the long history of the earth and for the long history of changing life forms whose remains are found in the rocks.
Learning Goal 3b
More recently deposited rock layers are more likely to contain fossils resembling existing species.
Learning Goal 4
Most species that have lived on the earth are now extinct. Extinction of species occurs when the environment changes and the individual organisms of that species do not have the traits necessary to survive and reproduce in the changed environment.
Learning Goal 5
Reproduction is necessary for the survival of any species.
For Grades: 9-12
Learning Goal 1
The basic idea of biological evolution is that the earth's present-day species are descended from earlier, distinctly different species.
Learning Goal 2
Molecular evidence substantiates the anatomical evidence for evolution and provides additional detail about the sequence in which various lines of descent branched off from one another.
Learning Goal 3
Natural selection provides the following mechanism for evolution: Some variation in heritable characteristics exists within every species; some of these characteristics give individuals an advantage over others in surviving and reproducing; and the advantaged offspring, in turn, are more likely than others to survive and reproduce. As a result, the proportion of individuals that have advantageous characteristics will increase.
Learning Goal 4a
Heritable characteristics can be observed at molecular and whole-organism levels—in structure, chemistry, or behavior.
Learning Goal 4b
Heritable characteristics influence how likely an organism is to survive and reproduce.
Learning Goal 5
New heritable characteristics can result from new combinations of existing genes or from mutations of genes in reproductive cells. Changes in other cells of an organism cannot be passed on to the next generation.
Learning Goal 6a
Natural selection leads to organisms that are well-suited for survival in particular environments.
Learning Goal 6b
Chance alone can result in the persistence of some heritable characteristics having no survival or reproductive advantage or disadvantage for the organism.
Learning Goal 6c
When an environment, including other organisms that inhabit it changes, the survival value of inherited characteristics may change.
Learning Goal 7
Modern ideas about evolution and heredity provide a scientific explanation for the history of life on Earth as depicted in the fossil record and in the similarities evident within the diversity of existing organisms.
Learning Goal 8
Life on earth is thought to have begun as simple, one-celled organisms about four billion years ago. Once cells with nuclei developed about a billion years ago, increasingly complex multi-cellular organisms evolved.
Learning Goal 9
Evolution builds on what already exists, so the more variety there is, the more there can be in the future. But evolution does not necessitate long-term progress in some set direction. Evolutionary change appears to be like the growth of a bush: Some branches survive from the beginning with little or no change; many die out altogether; and others branch repeatedly, sometimes giving rise to more complex organisms.
Learning Goal 10
The continuing operation of natural selection on new characteristics and in diverse and changing environments, over and over again for millions of years, has produced a succession of diverse new species.
