Sciences grade 9 semester 1

Movement

Taking action or changing position

Respiration

Releasing energy from food

Sensitivity

Detecting and responding to the environment

Growth

Increasing in size or number of cells

Reproduction

Producing offspring

Excretion

Removing waste products

Nutrition

Taking in nutrients for energy growth and repair

Cell

The basic unit of life

Levels of organization

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism

Prokaryote

Cell without a nucleus or membrane-bound organelles

Eukaryote

Cell with a nucleus and membrane-bound organelles

Cell membrane

Controls entry and exit of substances and maintains homeostasis

Nucleus

Stores DNA and controls all cell activities

Cytoskeleton

Provides structure and moves organelles

Rough ER

Makes proteins and has ribosomes

Smooth ER

Makes lipids and has no ribosomes

Ribosome

Site of protein synthesis

Golgi apparatus

Modifies and packages proteins

Lysosome

Breaks down waste using enzymes

Mitochondria

Produces energy through cellular respiration

Chloroplast

Does photosynthesis in plant cells

Cell wall

Provides structure and support

Vacuole

Stores water food or waste

Centriole

Helps in cell division

DNA

Genetic material called deoxyribonucleic acid

Base pairs

A pairs with T and C pairs with G

Hydrogen bonds

Bonds that hold DNA base pairs together

Nucleotide

Sugar + phosphate + nitrogen base

Sugar-phosphate backbone

Outer structure of DNA made of phosphodiester bonds

Purines

A and G double-ring bases

Pyrimidines

T and C single-ring bases

Double helix

The twisted ladder shape of DNA

Chromosome

Coiled DNA and protein

Human chromosomes

46 chromosomes in 23 pairs

Autosomes

Chromosomes 1 through 22

Sex chromosomes

XX or XY

Gene

A DNA segment that codes for a trait

Allele

A version of a gene

Dominant allele

Capital letter that masks recessive

Recessive allele

Lowercase letter expressed only when homozygous

Homozygous

Two same alleles

Heterozygous

Two different alleles

Genotype

Genetic makeup such as BB Bb bb

Phenotype

Physical trait such as brown eyes

Punnett square

Tool for predicting genetic crosses

Bb × Bb ratio

Genotype 1 BB : 2 Bb : 1 bb

Phenotype ratio

3 dominant : 1 recessive

Mitosis

Cell division for growth and repair producing identical cells

Interphase

Where DNA replicates in S phase

Chromosomes after S phase

46 chromosomes 92 chromatids

Stages of mitosis

Prophase Metaphase Anaphase Telophase

Result of mitosis

Two identical daughter cells

Meiosis

Cell division to form gametes

Meiosis chromosome number

23 chromosomes (haploid)

Number of divisions

Two divisions Meiosis I and II

Crossing over

Exchange of DNA increasing variation

Independent assortment

Random chromosome separation

Result of meiosis

Four genetically different gametes

Atomic number

number of protons in an atom

Atomic mass

number of protons plus neutrons

Isotopes

atoms of the same element with different numbers of neutrons or mass

Cation

a positively charged ion formed when an atom loses electrons

Anion

a negatively charged ion formed when an atom gains electrons

Nucleus

the center of the atom made of protons and neutrons

Electron shell

region around the nucleus where electrons are found

Metals

elements with low electronegativity that tend to lose electrons

Nonmetals

elements with high electronegativity that tend to gain electrons

Electronegativity

the power of an atom to attract electrons to itself

Ionic bond

a chemical bond where electrons are transferred between atoms

Covalent bond

a chemical bond where electrons are shared between atoms

Metallic bond

attraction between free-floating valence electrons and positive metal ions

Period

the horizontal rows on the periodic table that show the number of electron shells

Group

the vertical columns on the periodic table that show the number of valence electrons

Valence electrons

outermost electrons that determine bonding and ion formation

Nuclear symbol

a notation showing mass number on top and atomic number on the bottom of the element symbol

Noble gases

elements with full valence shells that are stable and unreactive

Halogens

very reactive nonmetals in group 17 that gain 1 electron

Alkali metals

very reactive metals in group 1 that lose 1 electron

Alkaline earth metals

reactive metals in group 2 that lose 2 electrons

Transition metals

metals in the middle of the periodic table that can form multiple charges

Chalcogens

group 16 elements that gain 2 electrons

Monatomic ion naming rule

ionic compounds always end in "-ide"

Ionic compounds

usually formed between metals and nonmetals

Covalent compounds

usually formed between two nonmetals

Single covalent bond

a bond formed when 1 pair of electrons is shared between atoms

Double covalent bond

a bond formed when 2 pairs of electrons are shared between atoms

Triple covalent bond

a bond formed when 3 pairs of electrons are shared between atoms

High melting point

property of metals

Low melting point

property of nonmetals

Mono

1

Di

2

Tri

3

Tetra

4

Penta

5

Hexa

6

Hepta

7

Octa

8

Nona

9

Deca

10