Objective 2: Living Systems and the Environment

Organism: a living thing (plant or animal

Competition: a struggle for a limited amount of resources; an organism must have a way to get what it needs (ex. food, water, oxygen) or it will die. Example – Plants in the jungle compete for sunlight.

Ecosystem: the mix of all living and nonliving things and conditions in an area (temperature, animals, plants, rocks, etc.)

Population: organisms that are the same species, live in the same area, and breed with each other

Habitat: area an organism lives in and gets what it needs

Niche: the role a species has in an ecosystem

Ecological Succession: gradual replacement of plants and animals over time due to environmental changes like a forest fire

Chromosome: structure found in cell’s nucleus; contains DNA

Allele: form of a gene that controls a characteristic

Dominant Trait: trait that appears when at least one dominant allele is inherited – represented by a capital letter Ex. – R

Recessive Trait: trait that appears when two recessive alleles are inherited – represented by a lower case letter Ex. – r

Genotype: Inherited combination of alleles; represented by two letters Ex. – RR, Rr, or rr

Purebred (Homozygous): when an organism has two of the same alleles for its genotype Ex. 2 dominant alleles or 2 recessive alleles

Hybrid (Heterozygous): when an organism has two different alleles for its genotype Ex. 1 dominant and 1 recessive allele

Phenotype: organism’s appearance based on its genotype Ex. – red petals on a flower

Examples of Genotypes and Phenotypes:

R represents the dominant allele for red flower petals and r represents the recessive allele for white petals

Genotype               Phenotype   Reason

RR (homozygous)   red petals two dominant alleles

Rr (heterozygous)  red petals   one dominant allele

rr (homozygous)   white petals            two recessive alleles

Example of a Punnett Square:

B is dominant allele for Brown hair

b is recessive allele for Blonde hair

 

Mother Bb x Father Bb

Possible Combinations in the Offspring:

Genotype   Phenotype

25%  BB     25% Brown

50%  Bb     50% Brown

25%  bb     25% Blonde

There is a ¾ or 75% chance the offspring will have brown hair, and a ¼ or 25% chance it will have blonde hair.

Traits: an organism’s characteristics (eye color, height)

Inherited Trait: characteristic passed from parent to offspring through genes

Heredity: the passing of traits from one generation to the next

Gene: piece of DNA that represents the basic unit of heredity

Adaptation: trait that helps an organism live and meet its needs better; organisms may use colors, smells, or poisons to blend into their habitat or protect themselves

Natural Selection: process by which organisms with certain favorable traits survive and reproduce more successfully than others

Roles of Organisms:

Type of Animal               Source of Food               Example

Herbivore                         plants                                cow

Carnivore                         animals                              wolf

Omnivore                        plants and animals              bear

 

Term               Role                                                 Example

Predator         hunts/eats other organisms                lion

Prey                 hunted as food                                 rabbit

Scavenger       gets food from dead animals           vulture

Producer         makes own food                              plants

Consumer       gets food from other organisms      animals

Decomposer   gets food from dead organisms       fungi                                                                                                 or the waste of organisms

 

 

Food Chain: describes how energy is passed from one organism to another; energy originates from the Sun and is passed to producers and then to consumers; energy moves in the direction of the arrow from one organism to the other

Food Web: picture that shows the many food chains in an ecosystem; arrows show the direction energy moves; energy originates from the Sun

Extinct: If a species cannot get what it needs, it will die out

Endangered: if a species cannot get what it needs, the number will get smaller and over time may become extinct

Human Impact: humans can change an ecosystem in bad ways Ex. – air or water pollution or in good ways Ex. – Conservation

Interaction among systems: often many systems must interact to perform a function

Example: In the human body – A person can exercise only because several organs and organ systems interact.  A person (using his/her brain) decides to exercise.  The nervous system sends a signal to the muscles to begin moving.  The circulatory system begins pumping blood faster to provide more oxygen to the body.

Homeostasis: ability of an organism or its systems to maintain internal equilibrium (stability or balance) using chemical reactions and physical processes (feedback mechanisms)

Example: When the body temperature is too hot the body will begin to sweat, blood vessels dilate (get bigger) to allow heat out.

Photosynthesis: plants transform the Sun’s radiant energy (light) into chemical energy in the form of glucose (sugar) which is food for the plant.

6H₂O   + 6CO₂                         à       C₆H₁₂O₆ + 6O₂

Water + Carbon dioxide produces glucose + oxygen

Nitrogen Cycle

Nitrogen is needed by living things.  Bacteria change the nitrogen in the air into a form that plants can get and use from the soil.  Animals get nitrogen by eating plants.  Decomposers return nitrogen from dead plants and animals back to the soil.

Environmental Changes: changes in the environment can affect the survival of an organism or species Ex. – If a river dries up, the fish will die and the food supply for bears will decrease.  The bear population will decline unless the bears find a different food source.

Limiting Factors: factors that control a population Ex. – food, water, living space, shelter

Cell: smallest unit of living things

- All organisms are made of one or more cells

- Cells have functions (jobs) that help keep the organism alive

- Cells contain smaller structures that each have a function (cell wall and chloroplasts are structures that are unique to plant cells)

Levels of Organization: Living things build and organize themselves from small and simple (atom) to complex systems (communities).

Mrs. Davis’

8th Grade Science