Key Concepts in Biology and Ecology

Characteristics of Living Organisms

Living organisms grow, reproduce, respond to stimuli, maintain homeostasis, metabolize energy, and are made of cells.

Prokaryotic vs Eukaryotic Cells

Both have a plasma membrane, cytoplasm, and genetic material. Prokaryotes lack a nucleus and organelles; eukaryotes have them.

Differences between Plant and Animal Cells

Plant cells have a cell wall, chloroplasts, and large central vacuoles. Animal cells do not.

Major Organelles and Their Functions

Nucleus (DNA storage), mitochondria (energy production), ribosomes (protein synthesis), ER (protein/lipid processing), Golgi apparatus (packaging), chloroplasts (photosynthesis, in plants), vacuoles (storage).

Types of Moving Appendages in Cells

Cilia (e.g., respiratory cells), flagella (e.g., sperm cells).

Basic Structure of Atoms

Atoms have a nucleus (protons, neutrons) and electrons. They form bonds to create molecules needed for life.

Hydrolysis vs Dehydration Synthesis

Hydrolysis breaks bonds by adding water; dehydration synthesis forms bonds by removing water.

Classes of Biological Macromolecules

Carbohydrates (energy), lipids (storage/insulation), proteins (structure/enzymes), nucleic acids (genetic info).

Digestive System Organs and Food Processing Stages

Alimentary canal: mouth, esophagus, stomach, intestines. Accessory organs: liver, pancreas, gallbladder. Stages: ingestion, digestion, absorption, elimination.

Energy Transport Systems in the Body

Digestive system breaks down food; circulatory system transports nutrients; respiratory system provides oxygen for cellular respiration.

Cellular Respiration Process

Glycolysis (cytoplasm), Krebs cycle (mitochondrial matrix), and ETC (mitochondrial membrane) produce ATP.

Aerobic vs Anaerobic Cellular Respiration

Aerobic uses oxygen; anaerobic does not and produces less ATP.

Structural Hierarchy of Human Body Systems

Cells → Tissues (epithelial, connective, muscle, nervous) → Organs → Systems.

Components of the Immune System

Components: white blood cells, lymph nodes, spleen, antibodies. Autoimmune attacks can destroy insulin-producing cells, causing diabetes.

Main Organs of the Endocrine System

Organs: pituitary, thyroid, pancreas, adrenal glands. Hormones regulate growth, metabolism, and homeostasis.

Regulation of Blood Glucose Levels

Insulin lowers glucose; glucagon raises it. Diabetes occurs when insulin production or response fails.

Types of Diabetes

Type 1: autoimmune, no insulin. Type 2: insulin resistance. Gestational: during pregnancy.

Main Organs of the Respiratory System

Organs: nose, trachea, lungs, alveoli. Oxygen is absorbed, CO₂ is expelled in alveoli.

Circulatory System Function

Heart pumps blood through arteries, veins, and capillaries, delivering oxygen/nutrients and removing waste.

Circulatory System Issues

Issues: heart attacks, strokes, hypertension, atherosclerosis.

Importance of Fats and Lipids

Fats store energy, insulate, and are vital for cell membranes and hormone production.

Cholesterol Types

Cholesterol: fat-like substance. LDL (bad) clogs arteries; HDL (good) removes excess.

Saturated vs Unsaturated Fats

Saturated: solid, raises LDL. Unsaturated: liquid, improves heart health.

Reasons for Cell Division

Growth, repair, reproduction.

Sexual vs Asexual Reproduction

Sexual: two parents, genetic diversity. Asexual: one parent, identical offspring.

Structure and Function of Chromosomes

Chromosomes: DNA-protein structures, carry genetic information.

Cell Cycle Phases

Interphase: growth/DNA replication. Mitosis: prophase, metaphase, anaphase, telophase. Cytokinesis: cell splits.

Cancer Origin from Normal Cells

Mutations disrupt cell cycle regulation, leading to uncontrolled division.

Lymphocytes and Their Functions

Lymphocytes: white blood cells. B cells make antibodies; T cells destroy infected cells.

How Antibiotics Work

Antibiotics target bacterial structures like cell walls or ribosomes.

Natural Selection Process

Favorable traits increase survival/reproduction, spreading over generations.

Evidence for Evolution by Natural Selection

Examples: antibiotic resistance, finch beaks. Evidence: fossils, genetic similarities.

Artificial Selection

Artificial selection: humans breed for traits, e.g., dog breeds.

Genetic Material Transfer in Bacteria

Transformation, transduction, conjugation.

Bacterial Resistance to Antibiotics

Mutations or acquiring resistance genes via horizontal gene transfer.

Viruses and Life

Viruses cannot reproduce or metabolize without a host.

Basic Structures of a Virus

Viruses consist of genetic material (DNA or RNA), a protein coat (capsid), and sometimes a lipid envelope.

Lytic vs Lysogenic Cycles of Viruses

In the lytic cycle, viruses replicate inside the host cell and cause it to burst, releasing new viruses. In the lysogenic cycle, the viral DNA integrates into the host genome and replicates with it without causing immediate harm.

Defensive Elements of the Immune System

1. Physical barriers (e.g., skin, mucous membranes). 2. Innate immunity (e.g., inflammation, phagocytes). 3. Adaptive immunity (e.g., B cells, T cells). 4. Support systems (e.g., lymphatic system).

External Barriers Protecting from Pathogens

Skin, mucous membranes, saliva, tears, and stomach acid.

Inflammatory response

It increases blood flow, brings immune cells to the infection site, and helps isolate and destroy pathogens.

Lymphatic system

The lymphatic system transports lymph, filters pathogens, and houses lymphocytes (B and T cells).

Non-specific immunity

General defenses like skin and inflammation.

Specific immunity

Targeted response by B and T cells.

Antigen

A foreign molecule that triggers an immune response.

Lymphocyte

White blood cells (e.g., B and T cells) involved in specific immunity.

B cells

Produce antibodies.

Helper T cells

Activate B and T cells.

Cytotoxic T cells

Destroy infected cells.

Memory cells

Provide long-term immunity by recognizing previously encountered pathogens.

Vaccines

Introduce a harmless form of a pathogen, triggering the immune system to produce memory cells and antibodies.

Virus mutation

Viruses mutate, altering their antigens, which may reduce vaccine effectiveness and require updates to vaccines.

Double-blind design

Ensures neither participants nor researchers know who receives the treatment or placebo, reducing bias.

Coronavirus

Coronaviruses are a family of RNA viruses that cause respiratory illnesses. Examples include SARS-CoV, MERS-CoV, and SARS-CoV-2 (COVID-19).

Moderna/Pfizer vaccines

mRNA vaccines that instruct cells to produce the viral spike protein, triggering immunity.

Johnson & Johnson vaccine

A viral vector vaccine using a modified adenovirus to deliver spike protein instructions.

Meiosis I

Homologous chromosomes separate, reducing the chromosome number by half.

Meiosis II

Sister chromatids separate, producing four haploid gametes.

Genetic variation mechanisms

1. Crossing over during meiosis. 2. Independent assortment of chromosomes. 3. Random fertilization.

Mitosis

Produces two identical diploid cells for growth and repair.

Meiosis

Produces four non-identical haploid cells for reproduction.

Nondisjunction

Occurs when chromosomes fail to separate during meiosis, leading to gametes with abnormal chromosome numbers (e.g., trisomy 21).

Spermatogenesis

Testes produce sperm.

Oogenesis

Ovaries produce eggs.

Human development stages

1. Fertilization: Sperm and egg fuse to form a zygote. 2. Embryonic stage: Organ systems develop. 3. Fetal stage: Growth and maturation. 4. Birth: Delivery of the baby.

Infertility causes

Causes include hormonal imbalances, structural abnormalities, age, lifestyle factors, and genetic conditions.

Assisted reproduction

Techniques that help individuals conceive, such as IVF, artificial insemination, and ICSI.

Artificial insemination

Sperm is directly placed into the uterus.

In vitro fertilization (IVF)

Eggs are fertilized outside the body and implanted.

Intracytoplasmic sperm injection (ICSI)

A single sperm is injected into an egg.

Eukaryotic nucleus structure

The nucleus has a double membrane, contains chromatin (DNA + proteins), and organizes into chromosomes during cell division.

Dominant alleles

Expressed if present.

Recessive alleles

Expressed only when no dominant allele is present.

Non-Mendelian inheritance

Examples include incomplete dominance, codominance, and polygenic inheritance.

Sex-linked inheritance

Males have one X chromosome, so they express X-linked traits even if recessive, whereas females require two copies of the recessive allele.

Punnett square

Visualizes allele combinations to predict offspring genotypes and phenotypes.

Genetic pedigree

Tracks inheritance patterns of traits through family generations, showing dominant, recessive, or sex-linked traits.

Protein synthesis

1. Transcription: DNA is transcribed into mRNA in the nucleus. 2. Translation: mRNA is read by ribosomes in the cytoplasm to assemble proteins from amino acids.

Genetic disease categories

1. Single-gene disorders (e.g., cystic fibrosis). 2. Chromosomal disorders (e.g., Down syndrome). 3. Multifactorial disorders (e.g., heart disease). 4. Mitochondrial disorders (e.g., Leber's hereditary optic neuropathy).

Genetic disease diagnosis

Techniques include genetic testing, karyotyping, and biochemical tests.

DNA sequencing

Determines nucleotide order; DNA profiling compares unique DNA patterns for forensics and paternity.

Gene therapy

Aims to replace, inactivate, or introduce genes to treat genetic disorders.

Replication

Copies DNA, with each new molecule having one original and one new strand.

DNA synthesizer

Builds DNA sequences for analysis; DNA profilers use them to create DNA samples for comparison.

PCR

Polymerase Chain Reaction amplifies DNA.

Thermal cycler

Automates temperature changes for PCR.

Electrophoresis

Separates DNA fragments by size, creating a visible pattern for analysis.

Short tandem repeats (STRs)

Repetitive DNA sequences; their unique patterns identify individuals in forensic analysis.

CODIS

A database of DNA profiles used to match crime scene DNA to offenders.

Bioelements

Carbon, hydrogen, oxygen, and nitrogen.

Macronutrients

Needed in large quantities (e.g., nitrogen, phosphorus, potassium).

Micronutrients

Needed in small quantities (e.g., iron, zinc, copper).

Essential nutrient

A substance organisms need but cannot synthesize.

Plant examples of essential nutrients

Nitrogen, potassium, phosphorus.

Human examples of essential nutrients

Vitamins (e.g., C, D), amino acids, and minerals (e.g., calcium).

Genetically modified organisms (GMOs)

Created by inserting specific genes into an organism's DNA using biotechnology to improve traits like pest resistance, yield, or nutrition.

Benefits of genetically modified crops

Increased yield, pest resistance, reduced pesticide use, and enhanced nutrition.

Concerns associated with genetically modified crops

Environmental impact, loss of biodiversity, and ethical or health issues.

Biofuel

Renewable energy source made from organic materials.

Production of biofuels

Fermentation of crops (e.g., corn, sugarcane) or processing of algae and waste materials.