Grade 9 Biology

9th Grade Science with topics discussing: Cardiovascular System, Respiratory System, & Non-Mendelian Genetics

Gregor Mendel

Austrian scientist known as the Father of Genetics who discovered basic inheritance patterns using pea plants

Pisum sativum

Scientific name of the pea plant used in Mendel’s experiments

Law of Segregation

Principle stating that allele pairs separate during gamete formation so each gamete carries only one allele

Law of Independent Assortment

Principle stating that genes for different traits are inherited independently of each other (if not linked)

Punnett Square

Diagram used to predict possible genetic outcomes of a cross

Trait

A heritable characteristic (e.g., height, eye color)

Heredity

Transmission of traits from parents to offspring

Genetics

Study of heredity and variation in living organisms

Gene

Segment of DNA that codes for a specific trait

Allele

Alternative form of a gene

Dominant Allele

Allele that is expressed when present; written as a capital letter

Recessive Allele

Allele expressed only when two copies are present; written as lowercase

Genotype

Genetic makeup of an organism (e.g., BB, Bb, bb)

Phenotype

Observable physical traits of an organism

Homozygous

Having two identical alleles for a trait

Heterozygous

Having two different alleles for a trait

Chromosome

Threadlike DNA structure that carries genes

Mendelian Inheritance

Pattern of inheritance dominant and recessive allele rules

Incomplete Dominance

Inheritance pattern where heterozygous offspring show a blended phenotype

Codominance

Inheritance pattern where both alleles are fully expressed in the phenotype

Multiple Alleles

When a gene has more than two allele forms in a population

ABO Blood Group System

Blood typing system determined by three alleles: IA, IB, and i

Blood Type A

Genotype IAIA or IAi

Blood Type B

Genotype IBIB or IBi

Blood Type AB

Genotype IAIB (codominance)

Blood Type O

Genotype ii (recessive)

Sex Chromosomes

Chromosomes that determine biological sex (XX female, XY male)

Sex-linked Inheritance

Pattern of inheritance involving genes on sex chromosomes

Colorblindness

X-linked recessive condition affecting color vision

Hemophilia

X-linked recessive disorder where blood does not clot properly

Carrier

Individual who has one recessive allele for a trait but does not show the condition

Respiratory System

Organ system responsible for gas exchange (oxygen in, carbon dioxide out)

Respiration

Process of releasing energy from food using oxygen

Ventilation (Breathing)

Movement of air into and out of the lungs

External Respiration

Gas exchange between alveoli and blood

Internal Respiration

Gas exchange between blood and body cells

Lung Cancer

Uncontrolled growth of abnormal cells in lung tissue

Chronic Bronchitis

Long-term inflammation of the bronchi often caused by smoking

Smoking

Inhalation of tobacco smoke that damages the respiratory system

COVID-19

Respiratory disease caused by SARS-CoV-2 that can damage the lungs

Pneumonia

Infection that inflames alveoli and may fill them with fluid or pus

Olfaction

Sense of smell

Exhalation (Expiration)

Process of pushing air out of the lungs

Inhalation (Inspiration)

Process of taking air into the lungs

Diaphragm

Dome-shaped muscle below the lungs that controls breathing

Lungs

Main respiratory organs containing bronchi, bronchioles, and alveoli

Capillaries

Tiny blood vessels surrounding alveoli for gas exchange

Alveoli

Tiny air sacs where gas exchange occurs

Bronchioles

Smaller branches of the bronchi leading to alveoli.

Bronchi

Two main airways branching from the trachea into the lungs.

Trachea (Windpipe)

Tube that carries air to the bronchi

Epiglottis

Flap of cartilage that prevents food from entering the trachea

Larynx (Voice Box)

Organ containing vocal cords that produces sound

Pharynx

Passageway connecting nasal cavity to larynx

Cilia

Tiny hair-like structures that move mucus and trapped particles

Mucus

Sticky fluid that traps dust and pathogens

Nasal Cavity

Air passage that filters, warms, and moistens incoming air

Lower Respiratory System

Includes trachea, bronchi, bronchioles, alveoli, and lungs

Upper Respiratory System

Includes nasal cavity, pharynx, and larynx

Carbon Dioxide (CO₂)

Waste gas produced during cellular respiration

Oxygen (O₂)

Gas required by cells for energy production

Cellular Respiration

Process in cells that uses oxygen to produce energy (ATP)

Circulatory System

Body system responsible for transporting oxygen, nutrients, hormones, and wastes throughout the body

Cardiovascular System

The heart and blood vessels that circulate blood; often used interchangeably with circulatory system

Heart

Hollow, muscular organ that pumps blood throughout the body through rhythmic contractions

Blood

Connective tissue that transports substances throughout the body

Blood Vessels

Tubes that carry blood to and from the heart

Oxygen (O₂)

Gas delivered to cells for energy production

Carbon Dioxide (CO₂)

Waste gas produced by cells and removed through the lungs

Nutrients

Substances from food carried by blood to body cells

Hormones

Chemical messengers transported through blood from endocrine glands to target organs

Atria

The two upper chambers of the heart that receive blood

Right Atrium

Chamber that receives oxygen-poor blood from the body

Left Atrium

Chamber that receives oxygen-rich blood from the lungs

Ventricles

The two lower chambers that pump blood out of the heart

Right Ventricle

Pumps oxygen-poor blood to the lungs

Left Ventricle

Pumps oxygen-rich blood to the body; has the thickest wall

Septum

Muscular wall that separates the right and left sides of the heart

Heartbeat

One complete contraction and relaxation cycle of the heart

Vena Cava

Large vein that brings oxygen-poor blood from the body to the right atrium

Superior Vena Cava

Returns blood from the upper body

Inferior Vena Cava

Returns blood from the lower body

Pulmonary Artery

Carries oxygen-poor blood from the right ventricle to the lungs

Pulmonary Vein

Carries oxygen-rich blood from the lungs to the left atrium

Aorta

Largest artery that carries oxygen-rich blood from the left ventricle to the body

Left Side of Heart

Sends blood to body

Right Side of Heart

Sends blood to lungs

Capillaries

Exchange site

Veins

Toward heart

Arteries

Away from heart

Blood

Transport medium

Anemia

Condition with low red blood cell count or hemoglobin, reducing oxygen delivery

Stroke

Blockage or rupture of a blood vessel in the brain

Heart Attack (Myocardial Infarction)

Blockage of coronary artery cutting off oxygen to heart muscle

Plaque

Fatty deposits that accumulate in artery walls

Atherosclerosis

Buildup of plaque inside arteries causing narrowing

Hypertension

High blood pressure that can damage blood vessels

Waste Removal

Blood transports metabolic wastes to kidneys, liver, and lungs for elimination

Immune Defense

White blood cells in blood protect against pathogens

Temperature Regulation

Circulatory system helps maintain stable body temperature