Life Science

Review of Grade 6 Science

Classification of Organisms

Taxonomy – the science of describing, classifying, and naming living things

Carolus Linnaeus – the Swedish scientist who founded modern taxonomy

Classification System Kingdom (most general way to group organisms) Phylum Class Order Family Genus Species (most specific way to group

organisms)

The Five-Kingdom Classification System –

Monera Protista Fungi Plantae Animalia

Monera – Eubacteria (modern bacteria) & Archaebacteria (ancient bacteria)

include bacteria and blue-green algae have no nuclei oldest & most numerous organisms on

Earth

Protista

include amoebas and euglenas single cells and microscopic have nuclei but lack any specialized

tissues and organs commonly called protozoa

Fungi

includes mushrooms, yeasts, and molds yeasts are unicellular, but the rest are

multicellular decompose other organisms and are

important to maintain a healthy ecosystem

Plantae

includes mosses, ferns, flowers, and trees (multicellular organisms)

most red, brown, and green algae (single-celled organisms)

can make their own food by photosynthesis

cannot move about freely

Animalia

includes sponges, jellyfish, worms, shellfish, starfish, insects, fish, amphibians, reptiles, birds, mammals, and humans

multicellular organisms get energy by eating other organisms are able to move about freely

Key words –

invertebrate – animal without a backbone vertebrate – animal with a backbone

Structure and Function of Cells

All organisms are made up of cells. Cells are the building blocks of life.

Key words – unicellular – just one cell multicellular – many cells organelles – tiny structures in cells

Cell Organelles and their Functions

cell membrane plant & animal a semi permeable membrane that controls movement of molecules into and out of the cell

nucleus plant & animal the control center of the cell; contains chromosomes that carry the genes

nuclear

membrane

plant & animal a semi permeable membrane; encloses and protects the nucleus

vacuoles plant & animal storage sac that contains fluids, pigments, and other substances

mitochondria plant & animal the powerhouse of the cell; releases energy to support all cell activities

endoplasmic

reticulum

plant & animal system of tubules inside the cytoplasm for transport of materials

cytoplasm plant & animal clear, thick fluid that holds all the organelles in a cell

ribosomes plant & animal contain enzymes that help make proteins

chloroplasts plant contain chlorophyll; where photosynthesis happens

cell wall plant the outer non-living cellulose structure that helps the cell keep its shape

Key Terms –

Mitosis – the process of one cell dividing into two equal and identical cells; makes body cells

Meiosis – the process of one cell divides two times to make sex cells with half the number of chromosomes of a body cell

Photosynthesis

the process that plants use to capture energy from the sun and change it into food

happens in the chloroplast chlorophyll, a green pigment in leaves, converts

sunlight into food carbon dioxide, water, and sunlight energy is

turned into sugar or food (glucose) and oxygen

Cellular respiration

the process used by complex organisms, such as humans, to get energy from food

happens in the mitochondrion food-sugar (glucose), oxygen is turned into

carbon dioxide, water, and energy (ATP)

Reproduction and Heredity

Reproduction – involves creating an entire organism

Two Methods of Reproduction –

Asexual reproduction

Sexual reproduction

Asexual reproduction –

the offspring (young) has only one parent the offspring are clones of their single

parent by mitosis (exact copies of the original cell)

algae, bacteria, strawberries (runners), tubers (white potatoes), bulbs (tulips, onions), regeneration (planaria, starfish)

Sexual reproduction –

the offspring has two parents the offspring form when a sperm and an egg

join by a process called fertilization offspring have some of the traits of both

parents and other traits not visible in the parents but nonetheless present offspring

the offspring have genetic material from both parents

The nucleus -

contains the organism’s genetic material contains 46 chromosomes (threadlike

strands of DNA that carry the code or genes telling the traits the organisms will have)

Gametes –

are the sex cells (eggs and sperm) contain 23 chromosome (half the number

of chromosomes found in a body cell) made in the reproductive organs made by a process called meiosis (the

number of chromosomes in the gamete is reduced by half)

Key Terms –

dominant trait – the trait that appears in an offspring when two different genes are mixed

recessive trait – the trait that does not appear when two different genes are mixed; for a recessive trait to be seen, two recessive genes must be present

zygote – is the single cell formed when the egg and sperm unite; a fertilized egg

embryo – is the name of the fertilized egg once it begins dividing by mitosis

variation – differences in traits among individuals of a species

Systems of Living Things

organized differentiated

Organization of Living Things

cells tissues organs

organ system organism

Organ Systems and their FunctionsCirculatory the blood carries food, oxygen, and nutrients to all areas of

the body

Digestive breaks down food and absorbs nutrients

Endocrine uses chemical hormones to control other body systems

Excretory gathers the wastes from the digestive, respiratory, and circulatory systems and discharges them from the body

Immune protects us from disease - using the skin as a barrier to the outside world and using white blood cells and antibodies

Muscular allows body movement, maintains posture, moves food

Nervous controls and coordinates; carries nerve messages to and from the brain and spinal cord and rest of the body

Reproductive takes its signals from certain hormones to make sex cells to allow offspring to be produced

Respiratory brings oxygen in and removes carbon dioxide from body

Skeletal Protects, supports, allows movement, makes blood cells, and stores minerals

Evolution and Biodiversity

evolution – the process in which inherited characteristics within a population change over generations such that new species sometimes arise

heredity – your characteristics that make up your physical body are handed down to your through the genetic material from your ancestors

variation – differences in traits among individuals of a species

adaptations – a characteristic or trait that improves an individual’s ability to survive and reproduce

natural selection or survival of the fittest – the most fit organisms will survive and reproduce and pass their good traits to their offspring

Organisms and the Environment ecology – the study of the relationship of living things to

the environment

ecosystem – the living community of organisms and their nonliving environment

food chain – a way of showing the order in which food energy passes from one organism to another

food web – two or more food chains

niche – the job or role an organism plays

competition – when organisms struggle with one another to get the things they need to survive

Key Terms prey – the animal that is eaten predator – an animal that eats other animals parasite – an organism that lives off another

organism host – the organism that provides a home for

another organism socialization – when a species live together in

groups to care and protect their young; primates, whales

cooperation – when organisms work together; wolves, lions, whales

Symbiosis

organisms from different species work together in groups and form partnerships that help the organisms involved

Three types of Symbiosis:

mutualism – a form of symbiosis in which both organisms benefit

commensalism – a form of symbiosis in which one organism benefits and the other is not harmed

parasitism – a form of symbiosis in which one organism benefits and the other is harmed

Food Levels Producers

Consumers Decomposers

These food levels are used to show how far an organism is from the primary source of all food energy, the Sun. The closer an organism’s food source is to the Sun, the more numerous the organism.

Producers

make their own food all green plants, phytoplankton

(microorganisms in the ocean), algae

Consumers – eat other organisms primary consumers (herbivores) - eat only

plants or parts of plants

secondary consumers (carnivores) – eat herbivores or other carnivores

omnivores – (primary & secondary consumers) - eat both plant & animals

Decomposers

break down dead organisms recycle nutrients bacteria, earthworms, and fungi

Changes in Ecosystems over Time abiotic – nonliving factors in the environment

biotic factors – living factors in the environment

biome – a large area of land that has the same climate

biodiversity – the variety in the types of organisms that live in an area

catastrophic disturbance – unexpected events such as volcanic eruption, forest fires

Key Terms eutrophication – when extra nutrients get into a

river, lake, or bay, they cause unusual algae growth. When too many aquatic organisms, such as algae, grow in a body of water, they deplete the level of oxygen in the water so that other organisms cannot live

phototropism – the tendency of plants to bend or lean toward light in order to get the most energy from photosynthesis

succession – a series of changes in a living community

climax community – a stable community at the end of succession