LIFE SCIENCE

FROM MOLECULES TO ORGANISMS: STRUCTURES AND PROCESSES

Structure and Function

All organisms have external parts. Different animals use their body parts in different ways to see, hear, grasp objects, protect themselves, move from place to place,

and seek, find, and take in food, water, and air. Plants also have different parts (roots, stems, leaves, flowers, fruits) that help them survive and grow.

Plants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction.

Structure and Function

All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different

numbers and types of cells (multicellular).

Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.

In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and

organs that are specialized for particular body functions.

Structure and Function

Systems of specialized cells within organisms help them perform the essential functions of life.

All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for

the formation of proteins, which carry out most of the work of cells.

Multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a

component of the next level.

Feedback mechanisms maintain a living system's internal conditions within certain limits and mediate behaviors, allowing it to remain

alive and functional even as external conditions change within some range. Feedback mechanisms can encourage

(through positive feedback) or discourage (negative feedback) what is going on inside the living system.

Growth and Development of Organisms

Reproduction is essential to the continued existence of every kind of organism. Plants and animals have unique and diverse life cycles.

Food provides animals with the materials they need for body repair and growth and the energy they need to maintain body warmth and for motion.

Plants acquire their material for growth chiefly from air and water.

Growth and Development of Organisms

Organisms reproduce, either sexually or asexually, and transfer their genetic information to their offspring.

Animals engage in characteristic behaviors that increase the odds of reproduction.

Plants reproduce in a variety of ways, sometimes depending on animal behavior and specialized features for reproduction.

Genetic factors as well as local conditions affect the growth of the adult plant.

Growth and Development of Organisms

In multicellular organisms, individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The

organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell

passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division

and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work

together to meet the needs of the whole organism.

Organization for Matter and Energy Flow in Organisms

All animals need food in order to live and grow. They obtain their food from plants or from other animals. Plants need water and light to live and grow.

Organization for Matter and Energy Flow in Organisms

Plants, algae (including phytoplankton) and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water

through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use.

Within individual organisms, food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules, to support growth

or to release energy.

Organization for Matter and Energy Flow in Organisms

The process of photosynthesis converts light energy to stored chemical energy by converting carbon dioxide plus water into sugars

plus released oxygen.

The sugar molecules thus formed contain carbon, hydrogen, and oxygen: their hydrocarbon backbones are used to make amino

acids and other carbon-based molecules that can be assembled into larger molecules (such as proteins or DNA)

used for example, to form new cells.

As matter and energy flow through different organizational levels of living systems, chemical elements are recombined in different

ways to form different products.

As a result of these chemical reactions, energy is transferred from one system of interacting molecules to another and release

energy to the surrounding environment and to maintain body temperature. Cellular respiration is a chemical process

whereby the bonds of food molecules and oxygen molecules are broken and new compounds are formed that

can transport energy to muscles.

Information Processing

Animals have body parts that capture and convey different kinds of information needed for growth and survival. Animals respond to these inputs with behaviors that

help them survive. Plants also respond to some external inputs.

Different sense receptors are specialized for particular kinds of information, which may be then processed by the animal's brain. Animals are able to use their

perceptions and memories to guide their actions.

Information Processing

Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain.

The signals are then processed in the brain, resulting in immediate behaviors or memories.