TAKS objective 2 Living Systems environment Middle School

TAKS objective 2 Living Systems & environment Middle School Science TAKS Need to Know

All living things are made up of cells. Unicellular (Single-celled)organisms that are made up of only one cell. Multicellular- organisms made up of many cells. (Some have billions & trillions of cells!)

Cells Most basic part of a living system “Cells are Building Blocks” Cells contain organelles Animal & Plant cells both contain: nucleus- command center of the cell membrane- protective outer layer cytoplasm- gelatin-like substance that fills inside of cell (contains other organelles that are vital to the processes of life) mitochondria- to provide power for cell activities

Only plant cells have cell walls for support & chloroplasts to carry out photosynthesis.

Animal Cell

Plant Cell Contain 2 organelles that animal cells do not have: *Chloroplastsuse sunlight & CO 2 to create food for the plant’s cells *Cell wall- rigid structure that provides protection and support for plant cell

Systems work together to carry out various life functions. Example: A track runner has different systems that work together: -Muscles move the arms & legs. This uses up oxygen, which must be provided through the bloodstream. -The heart starts beating faster to move more blood to the muscle cells that need oxygen. -As breathing rate increases, the lungs have to take in oxygen & get rid of carbon dioxide more quickly. -The brain sends signals to the lungs, heart, & muscles to coordinate all these activities.

Levels of Organization

Feedback mechanism A response of an organism to a given change, such as temperature or the amount of light. Example: Sweating If the body temperature gets too high, sweat glands open up, causing a person to sweat. The sweat then evaporates, carrying heat energy away from the body. This cools the skin. When the body temperature returns to normal, another nerve signal is sent out to

Cells, Tissues, Organ Systems When you breathe, cells in your lungs help move oxygen into your bloodstream. Many of these cells together form an air sac, which is a kind of lung tissue. These & other tissues together form a lung, which is an organ. The mouth, nose, & trachea are other organs that work together with the lungs to help you breathe. These are some of the organs that make up the respiratory system. The respiratory system is just one of the many organ systems in the whole human organism.

Homeostasis The body has ways of adjusting to different conditions. Keeping conditions such as body temperature constant is called equilibrium or homeostasis. Equilibrium occurs when a system is balanced. Adaptations What if a change is too extreme & an organism can’t maintain equilibrium? The organism may die!! However, most organisms are adapted to the environments where they live. Their body systems & behaviors adjust or change to allow them to survive in the new environment.

Extinction The loss of an entire species is called extinction. Example: If an organism doesn’t have adaptations that allow it to live in a colder climate, then it must move to a warmer environment or it will die. This can affect single organisms as well as whole populations.

Genetic traits Genes- a segment of DNA on a chromosome that contains information for specific genetic traits. Genes are passed from parents to offspring. Genetic trait- a characteristic passed on from a parent to offspring. Genetic traits that help organisms to survive in their environment are called adaptations. Adaptations can be either physical characteristics or behaviors.

How are genes passed from parents to offspring? During reproduction, the parents’ genes in the sex cells (egg & sperm) will create the new organism. This is called sexual reproduction. In sexual reproduction, both parents pass the genes for traits on to their offspring. Half the genes come from the male and half come from the female. Sexual reproduction results in genetic diversity due to the large number of gene combinations that may occur.

Each parent has genes that occur in pairs and, due to the production of the special sex cells, only one of the alleles of a gene pair will be in each sex cell. Alleles are forms of the same gene. So the offspring receive one allele of a gene from the mother and one from the father. Genes combine to produce different traits Alleles occur in two forms: dominant and recessive. If a dominant allele of a gene is present, the dominant trait will appear in the organism. A capital letter is used to show a dominant allele. For a recessive trait to be expressed, both alleles of the gene must be recessive. A lowercase letter is used to show a recessive trait. A pea plant will have purple flowers if it receives a dominant allele from one or both parents (Pp or PP). A plant will have white flowers only when both parents contribute an allele for the recessive trait (pp).

Ecosystem – includes the living & nonliving parts of an environment. Nonliving- water, soil, light, air Living- plants, animals & other living organisms (makes up the community) Community – a group of different types or populations or plants, animals, & other organisms living & interacting with one another in an environment. Each population in a community lives in a particular part of that environment called a habitat. As you move up the diagram, each level is more complex. A habitat is the specific place in which an organism makes its home.

Each part of the community has its own function, but together they form the entire pond ecosystem. Organisms are connected by the energy that flows through the pond community. Both plants & animals require energy. This flow begins with the plants using energy from the sun and continues through all the organisms in an ecosystem.

Plants change radiant energy from the sun into chemical energy. Carbon dioxide and water are converted into sugar and oxygen. (Sugar is very important in an ecosystem- it’s food for plants & for other organisms. When plants are eaten, the energy in the plant matter is passed on to other organisms in the food chain. )

Chemical energy passes from plants to animals through a food chain Producers- (plants) organisms that make their own food Primary consumers- animals that get their energy from eating plants Secondary (second-order) consumersanimals that eat primary consumer animals.

Animals can be both a primary & secondary consumer.

Types of consumers Herbivores- animals that eat only plants Carnivores- animals that eat only other animals Omnivores- animals that eat both plants & other animals

Decomposers Organisms that feed on dead plants & animals. This releases the chemical energy and nutrients in the dead plants and animals back into the environment. Decomposers play an important role in recycling nutrients & energy.

Food Chain- shows the flow of energy from one organism to another to yet another.

Food Web Energy passes in many different directions through all the organisms. A complex system of energy flow through overlapping food chains.

Succession Rebuilding of populations in a community or ecosystem that has been changed. Succession can happen in any environment where change occurs. Other examples: a plowed farm field, a burned forest, or a grassland that gradually receives less rainfall.

Systems in the Human Body The human body includes systems such as: Circulatory Respiratory Digestive Excretory Muscular Skeletal Nervous

Circulatory system Arteries are tubes that carry blood away from the heart Veins are tubes that return blood to the heart Capillaries connect arteries and veins. They are tiny tubes that exchange food, oxygen and wastes between blood and body cells.

Respirator y BREATH IN -- your body gets oxygen from the air. Rib muscles contract to pull ribs up and out. The DIAPHRAGM muscle contracts to pull down the lungs. Tissue expands to suck in air. BREATH OUT -- you get rid of other gases that your body does not need. Rib muscles relax. The Diaphragm muscle relaxes. Tissue returns to resting position and forces air out.

Digestive system Breaks down and absorbs food to provide energy for the body

Excretory Gets rid of body wastes and excess fluids

Muscles Muscle contracts to move bones and body parts Muscles look either striated or smooth: Striated muscle has stripes or striations in it. Smooth muscle does not.

Voluntary or Involuntary Muscles Voluntary muscles are muscles that you can move whenever you want to. Involuntary muscles contract and relax automatically inside your body. We can not control our involuntary muscles

Did you know? ? ? There are more than 600 muscles in your body That nearly 35 -40% of your body mass is muscle The smallest bones are in your ear. The largest bone, the femur, is found in your thigh

Skeletal system Function of bones protect internal organs support the body make blood cells store minerals provide for muscle attachment

Joints A point where one bone attaches to another bone. There are two different types of joints in the body: Movable joints (like ball-and-socket, hinge, gliding and pivot joints) Immovable joints (like the bones of the skull and pelvis) which allow little or no movement

Nervous system collects, transfers and processes information with brain, spinal cord, peripheral nerves, and nerves

Systems A group of parts that form a complex whole- work together to achieve goals that the parts could not reach alone. Parts can interact, be related to one another, or depend on each other. Example: Circulatory and Respiratory systems work together