Biology Concepts: Cell Cycle, Animal Systems, and Plant Structure
The Cell Cycle
Purpose: Growth, repair, and reproduction of cells.
Stages:
Interphase – Cell grows, DNA replicates, organelles duplicate
- G1: Growth
- S: DNA synthesis
- G2: Prep for division
Mitosis (M phase) – Division of the nucleus
Cytokinesis – Division of cytoplasm; two daughter cells form
Mitosis
Purpose: To produce identical daughter cells for growth and repair.
Phases:
Prophase – Chromosomes condense, spindle fibers form, nuclear membrane breaks down
Metaphase – Chromosomes line up at the cell center
Anaphase – Sister chromatids separate to opposite poles
Telophase – Nuclear membranes reform, chromosomes decondense
Cytokinesis – Cytoplasm divides, two identical cells form
Tip: Animal cells pinch in (cleavage furrow), plant cells form a cell plate.
Cancer
- Definition: Uncontrolled cell division
- Causes: Mutations in DNA, smoking, radiation, viruses
- Harmful because: Tumors can invade tissues, disrupt organ function
- Tumor types:
- Benign: Does not spread
- Malignant: Spreads (metastasizes)
- Screening: Mammograms, colonoscopies, Pap tests
- Treatment: Surgery, chemotherapy, radiation
- Prevention: Healthy lifestyle, avoiding carcinogens
Diffusion and Osmosis
- Diffusion: Movement of molecules from high $\rightarrow$ low concentration (e.g., oxygen into cells)
- Osmosis: Movement of water across a semi-permeable membrane (high $\rightarrow$ low water concentration)
- Relevance: Occurs in cells for nutrient uptake, waste removal, and maintaining water balance
Animal Organ Systems
Levels of Structural Organization
Cells – basic unit of life
Tissues – group of similar cells
Organs – different tissues working together
Organ systems – organs working together
Organism – entire living being
Stem Cells
- Definition: Unspecialized cells that can become other cell types
- Embryonic stem cells: Can become any cell (pluripotent)
- Tissue/adult stem cells: Can become limited cell types (multipotent)
Digestive System
Purpose: Break down food for energy and nutrients.
Organs: Mouth $\rightarrow$ Esophagus $\rightarrow$ Stomach $\rightarrow$ Small intestine $\rightarrow$ Large intestine $\rightarrow$ Rectum $\rightarrow$ Anus.
Accessory organs: Liver, pancreas, gallbladder.
- Interaction with circulatory system: Nutrients absorbed in small intestine $\rightarrow$ enter bloodstream $\rightarrow$ delivered to body cells.
- Disorders: Ulcers, constipation, Crohn’s disease.
Circulatory System
Purpose: Transport oxygen, nutrients, and wastes.
Components:
- Heart: Pumps blood
- Lungs: Oxygenate blood
- Arteries: Carry blood away from heart
- Veins: Carry blood to heart
- Capillaries: Exchange gases, nutrients, wastes
- Blood components:
- RBCs: Carry oxygen
- WBCs: Fight infection
- Platelets: Clot blood
- Plasma: Transport nutrients and hormones
Path of blood: Body $\rightarrow$ Right atrium $\rightarrow$ Right ventricle $\rightarrow$ Lungs $\rightarrow$ Left atrium $\rightarrow$ Left ventricle $\rightarrow$ Body.
Disorders: Arteriosclerosis (hardening of arteries), heart attacks.
Respiratory System
Purpose: Exchange gases (O₂ in, CO₂ out).
- Breathing vs. respiration: Breathing = movement of air; respiration = chemical process producing energy.
- Air pathway: Nose/mouth $\rightarrow$ pharynx $\rightarrow$ trachea $\rightarrow$ bronchi $\rightarrow$ bronchioles $\rightarrow$ alveoli.
- Cilia: Trap dust and move it out of airways.
- Gas exchange: O₂ diffuses from alveoli $\rightarrow$ capillaries; CO₂ diffuses from capillaries $\rightarrow$ alveoli.
- Disorders: Asthma, pneumonia, bronchitis.
Plants
Root and Shoot Systems
- Roots: Anchor plant, absorb water/nutrients.
- Shoots (stems, leaves, flowers): Support, transport, reproduction.
Plant Tissues
Dermal tissue: Outer layer, protection.
Vascular tissue: Xylem (water up), Phloem (food down).
Ground tissue: Photosynthesis, storage, support.
Leaf Anatomy
- Function: Photosynthesis, gas exchange.
- Key structures:
- Epidermis (protection)
- Mesophyll (photosynthesis)
- Veins (xylem/phloem)
- Stomata (pores for gas exchange)
- Guard cells (open/close stomata)
Xylem and Phloem
- Xylem: Transports water and minerals upward.
- Phloem: Transports food (sugar) up and down.
Stomata
- Function: Gas exchange, transpiration.
- Open: During the day to let CO₂ in for photosynthesis.
- Close: At night or in drought to conserve water.
- Guard cells: Surround stomata, control opening and closing.
Plant Tissues (Repeated Section Removed for Conciseness)
Dermal tissue: Outer layer, protection.
Vascular tissue: Xylem (water up), Phloem (food down).
Ground tissue: Photosynthesis, storage, support.
Leaf Anatomy (Repeated Section Removed for Conciseness)
- Function: Photosynthesis, gas exchange.
- Key structures:
- Epidermis (protection)
- Mesophyll (photosynthesis)
- Veins (xylem/phloem)
- Stomata (pores for gas exchange)
- Guard cells (open/close stomata)
Xylem and Phloem (Repeated Section Removed for Conciseness)
- Xylem: Transports water and minerals upward.
- Phloem: Transports food (sugar) up and down.
Stomata (Repeated Section Removed for Conciseness)
- Function: Gas exchange, transpiration.
- Open: During the day to let CO₂ in for photosynthesis.
- Close: At night or in drought to conserve water.
- Guard cells: Surround stomata, control opening and closing.
Xylem and Phloem (Repeated Section Removed for Conciseness)
- Xylem: Transports water and minerals upward.
- Phloem: Transports food (sugar) up and down.
Stomata (Repeated Section Removed for Conciseness)
- Function: Gas exchange, transpiration.
- Open: During the day to let CO₂ in for photosynthesis.
- Close: At night or in drought to conserve water.
- Guard cells: Surround stomata, control opening and closing.