Notes, summaries, assignments, exams, and problems for Biology

Alright, let’s make Cell Structure & Cell Theory feel alive—less textbook, more story 👇

What is a Cell? The Mini City of Life

A cell is the tiniest unit of life—like a mini city that keeps everything running.
Your body isn’t one big thing; it’s a community of trillions of cells, each doing its own job but working together so you can breathe, think, move, and feel.

The Three Fundamental Rules of Cell Theory

Cell theory is basically biology’s ground rules. Three simple but powerful ideas:

1. All Living Things Are Composed of Cells

From a tiny bacterium to a giant banyan tree to you—everything alive is built from cells.
Some organisms have one cell, others have millions or trillions, but no cell = no life.

2. The Cell Is the Basic

Disease Detectives: Epidemiology and Surveillance

Types of Public Health Surveillance

Passive surveillance relies on healthcare providers to report cases, making it cost-effective but prone to underreporting. Active surveillance involves health agencies actively seeking reports to ensure accurate data collection, often used during outbreaks. Sentinel surveillance monitors specific health events through selected providers, offering detailed but limited data. Syndromic surveillance focuses on symptoms rather than confirmed diagnoses, using real-time data to detect outbreaks.

The Five Steps of Surveillance

• Data collection
• Data analysis
• Data interpretation
• Data dissemination
• Link to action

Pioneering Scientists in Medicine

• Robert Koch: Father of bacteriology;

Introduction to Kiwi Bird Weight Research

Purpose: This investigation could be useful in scientific research regarding the weight distribution of kiwi birds while considering their genders. For example, the Department of Conservation (DOC) might be interested in finding alternative ways to distinguish female from male kiwi birds. By identifying patterns in weight relative to gender, it may become easier to identify individuals during scientific studies.

Investigation Question

I wonder if the median weight (kg) for female kiwi birds is higher than the median weight (kg) of male kiwi birds from the population of 700 kiwi birds observed in New Zealand in 2020.

Hypothesis and Biological Context

According to the Whakatane Kiwi Trust, "the female is 20... Continue reading "Sexual Dimorphism and Weight Analysis of Kiwi Birds" »

1. Homeostasis and Ecology

• 1(a) Maintaining constant internal conditions.
• 1(b) 250 hours.
• 1(c)(i) A.
• 1(c)(ii) Fertilisers from farms run off into rivers. This causes algal growth. Less light penetrates, reducing photosynthesis. Pesticides kill organisms.
• 1(d)(i) Low FSH: eggs do not mature.
• 1(d)(ii) Low LH: no ovulation.
• 1(e)(i) Less water is absorbed into the blood. Water moves by osmosis because water potential remains higher in the blood.
• 1(e)(ii) Mutation. Only resistant bacteria survive. They reproduce and pass on the allele.
• 1(f)(i) Denitrifying bacteria convert nitrate to nitrogen gas. This reduces algal growth, so there is more oxygen in rivers.
• 1(f)(ii) Roots absorb water. More transpiration occurs, leading to slower water flow and less runoff.

Antibody Functions

• Precipitation: Binds to soluble molecules so they become insoluble.
• Neutralization: Binds to and prevents the activity of viruses or toxins.

Fc Region Binding

• Phagocytes: Facilitates opsonization and stimulates cytokine release.
• Complement proteins: Stimulates complement fixation, which triggers MAC formation.

Diversity of Antibodies

• Each person has approximately 10²⁰ antibody molecules with millions of different specificities.
• It is likely that an antibody exists for any antigen a person might encounter.
• Mechanisms of diversity:
  • Genetic recombination: Combinations of hundreds of genes coding for heavy and light chains lead to millions of unique antibodies.
  • Somatic hypermutation: Diversity increases via a high rate of single base pair

Understanding Feeding and Nutrition

Feeding vs. Nutrition: Key Differences

• Feeding (Eating): Subjective, voluntary, and conscious actions related to consuming food.
• Nutrition (Nourishing): Involuntary, unconscious, and objective processes involving the assimilation of nutrients by the body.

Essential Nutrients: Organic and Inorganic

Nutrients are classified based on whether they contain carbon (C).

Inorganic Nutrients

These nutrients do not contain carbon (C). They are vital for bodily functions.

• Water: Essential for all chemical reactions in the body.
• Mineral Salts: Essential inorganic nutrients needed in small amounts.

Organic Nutrients

These nutrients contain carbon (C). They provide energy and building blocks for the body.

• Carbohydrates: Provide fast

Bone Lesions

Cemento-ossifying Fibroma

• Masses of poorly cellular cementum
• Fibro-cellular connective tissue

Central Giant Cell Lesion

• Multinucleated giant cells
• Areas of hemorrhage
• Loose vascular connective tissue rich in mononuclear cells

Facial Fibrous Dysplasia: Osseous Stage

• Dysplastic fibrous tissue
• Trabeculae of woven bone without peripheral osteoblastic rimming
• Trabeculae are equidistant from each other, taking the shape of C, U, or W letters (Chinese letter appearance)
• Retraction of dysplastic fibrous tissue from woven bone trabeculae
• Presence of blood vessels

Facial Fibrous Dysplasia: Osteoid Stage

• Trabeculae of osteoid bone laid down equidistant from each other
• Characteristic C, U, or W letter shapes and Chinese letter appearance

Malignant Neoplasms

Fibrosarcoma

• Malignant

Joints: Definition and Classification

A joint, also known as an articulation, is the point where two or more bones meet. Joints allow for movement, flexibility, and support in the skeletal system.

Classification of Joints

Joints can be classified based on their structure and function:

Structural Classification

1. Fibrous Joints: Held together by dense connective tissue (e.g., sutures in the skull).
2. Cartilaginous Joints: Connected by cartilage (e.g., intervertebral discs, symphysis pubis).
3. Synovial Joints: Characterized by a fluid-filled space between bones (e.g., hinge joints like the elbow, ball-and-socket joints like the shoulder).

Functional Classification

1. Synarthroses: Immovable joints (e.g., sutures in the skull).
2. Amphiarthroses: Slightly movable joints

Nervous and Endocrine Systems

The nervous system receives external and internal stimuli, interprets them, and decides an appropriate response. The response is executed by the effector organ or tissue. Nervous tissue is made up of cells called neurons.

Stimulus → Nervous System → Effectors → Muscles, Glands

Neuron Structure

• Cell body: The central part of the neuron.
• Dendrites: Extensions of the cell body. They receive the nerve impulse and transmit it to the cell body.
• Axon: A long fiber extending from the cell body. It transmits the nerve impulse to other neurons or effector cells.
• Myelin sheath: This layer protects the axon and increases the speed of the nerve impulse.
• Axon terminals: These are located at the end of the axon. They contain neurotransmitters,

1. Characteristics of Blood Vessels

1. Direction of flow:
   • Arteries: Away from the heart
   • Veins: Towards the heart
   • Capillaries: Between arteries and veins
2. Presence of valves:
   • Arteries: Absent
   • Veins: Present
   • Capillaries: Absent
3. Thickness of walls:
   • Arteries: Thick
   • Veins: Thin
   • Capillaries: Very thin
4. Pressure of blood flowing inside:
   • Arteries: High
   • Veins: Low
   • Capillaries: Low
5. Exchange of materials:
   • Arteries: Does not take place
   • Veins: Does not take place
   • Capillaries: Takes place

2. Labeling the Parts of the Heart

• A: Left ventricle
• B: Left atrioventricular (Bicuspid) valve
• C: Aortic semilunar valve
• D: Left atrium
• E: Pulmonary veins
• F: Left pulmonary artery
• G: Aorta
• H: Superior vena cava
• J: Pulmonary semilunar valve
• K: Right atrium
• L: Right atrioventricular (Tricuspid) valve
• M: Right