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

Plant Nutrition

Photosynthesis: The process by which plants manufacture carbohydrates from raw materials using energy from light.

Key Aspects of Photosynthesis and Respiration

• Chlorophyll: Transfers light energy into chemical energy stored in molecules, essential for the synthesis of carbohydrates.
• Carbohydrate Use and Storage: Aside from using complex carbohydrates to create the plant's structure, plants store carbohydrates or use them for energy to grow.
• Respiration: To utilize stored carbohydrates, plants take the glucose formed during photosynthesis and combine the carbohydrate with oxygen—a process called respiration—to release energy.
• Role of Chlorophyll and CO₂: Chlorophyll is required because it helps absorb the light needed for photosynthesis.

Respiratory System Components

• 1 Nose
• 2 Mouth
• 3 Larynx
• 4 Right lung
• 5 Right bronchus
• 6 Diaphragm
• 7 Pharynx
• 8 Trachea
• 9 Left bronchus
• 10 Bronchiole
• 11 Alveoli

Characteristics of Alveoli for Gas Exchange

The epithelium of the alveoli is monostratified, consisting of a single layer of extremely flattened epithelial cells. Similarly, the capillary epithelium consists of a single layer of flat cells, known as the endothelium. The alveoli are covered by a vast network of capillaries to facilitate efficient gas exchange.

How Air Is Cleaned, Moistened, and Warmed

The nose filters inhaled air using hairs that trap particles. Additionally, as air passes through the nasal cavity, it is warmed and moistened.

Understanding the Endothelium

The endothelium forms the thin walls... Continue reading "Human Respiratory and Digestive Systems: Key Functions" »

Understanding Inheritance and Continuous Variation

This type of inheritance refers to continuous characteristics regulated by genes that are inherited independently.

Sometimes, continuous variation does not only depend on one quantitative inheritance but also on the influence environmental factors have on the genotype. The height and weight of a population are classic examples of continuous characteristics that are affected by environmental factors.

Mendel's Laws of Inheritance

Mendel's First Law: Law of Uniformity

When two pure-bred individuals are crossed, all offspring of the first filial generation (F1) have the same genotype and phenotype.

Mendel's Second Law: Law of Segregation

When two individuals from the first filial generation are crossed,... Continue reading "Understanding Inheritance, Cell Theory, and the Origin of Life" »

Ovaries:

• Composed of ovarian follicles (sac-like structures)

Gametes

produced by gonads

Uterus:

• Located between the urinary bladder and rectum
• 3 layers: 1. Endometrium 2. Myometrium 3. Perimetrium
• Functions of the uterus:
  • Receives / retains a fertilized egg
  • Nourishes the fertilized egg

Penis:

• Delivers sperm into the female reproductive tract
• Regions:
  • Shaft
  • Glans penis (enlarged tip)
  • Prepuce (foreskin)
• Internally 3 areas of spongy erectile tissue around the urethra

Ovulation:

when the egg is mature the follicle ruptures

Haploid:

1N

Oocyte:

The oocyte is viable for 12 to 24 hours after ovulation

Sperm:

are viable for 12 to 48 hours after ejaculation

• Sperm cells must make their way to the uterine tube for fertilization to be possible

Fertilization:

When sperm nucleus... Continue reading "Female Reproductive System and Endocrine Glands" »

Traits are characteristics present in an organism that can be inherited by its offspring.

Homozygotes and Heterozygotes

• Two identical alleles (AA or aa): Homozygous
• Two different alleles (Aa): Heterozygous

A: Dominant allele

a: Recessive allele

Genotype is an organism's set of genes.

Phenotype is the way in which... Continue reading "Understanding Traits, Genes, and Mutations" »

The Urinary System and Excretion

Elimination of Waste Products

The urinary system plays a crucial role in eliminating waste products, including toxic substances produced during cellular metabolism, that are released into the blood.

Organs Involved in Excretion

• Kidneys (Urinary System)

  Eliminate toxic substances resulting from cell metabolism through urine.

• Lungs

  Eliminate carbon dioxide (resulting from cell metabolism: cell respiration).

• Liver

  Eliminates waste from digestion through bile, which is eventually eliminated with feces.

• Sweat Glands

  Eliminate waste* through sweat, a liquid similar to urine but more diluted.
  *Toxic substances resulting from cell metabolism.

Kidneys

Two bean-shaped organs located along the posterior wall of the abdominal cavity.... Continue reading "The Urinary System and Excretion: A Comprehensive Guide" »

Internal Environment and the Circulatory System

1.) Internal environment: Refers to the fluids that surround the cells in the body. Conditions of the internal environment, like temperature or the composition of the fluid, must be stable for cells to work properly. This stable internal environment, called homeostasis, is maintained by the organ systems of the body.

• The internal environment consists of:
• Interstitial fluid (tissue fluid): It surrounds and bathes the cells.
• Blood and lymph: They collect and distribute substances the cells need, and eliminate waste from the cells through the circulatory system.

The lymphatic system:

• Transport absorbed fat from the small intestine to the blood.
• Defend the body as part of the immune system.

Lymphatic System

2.

Homeostasis and Body Interaction

The interaction process fulfills two objectives:

• Adapt the body to changing conditions.
• Connect and coordinate the different parts of our body.

Homeostatic process is a series of different processes in which the body's stability is maintained. These processes allow the organs to maintain a balanced condition so they can function properly.

Components of the Nervous System Pathway

• The sensory organ: Receives information from the environment.
• The nervous system: Transforms the stimuli into nerve impulses.
• The effector organs: Receive the response from the nervous system.

Types of Effector Systems

1. Locomotor system: Formed of muscles and bones.
2. Endocrine system: Produces regulating hormones.

Neurons: Specialized Nerve Cells

Neurons... Continue reading "Human Body Homeostasis and Nervous System Function" »

DNA replication involves several steps:

1. Initiation: Initiator proteins bind to the origin of replication.
2. Unwinding: DNA helicase unwinds the DNA strands.
3. Single-strand binding: Proteins bind to exposed single-stranded DNA to keep them apart.
4. Topoisomerase: Moves ahead of replication fork and removes torque by making a double-stranded break in one DNA double helix and passing another segment of helix through it.
5. Primase: Lays down an RNA primer (10-12 nt long) that provides a 3’OH group to start synthesizing DNA.
6. Elongation: DNA polymerase III synthesizes DNA on both strands in the 5’-3’ direction. The leading strand is replicated continuously, while the lagging strand is replicated discontinuously.
7. Removal of RNA primers: DNA polymerase I removes

Meselson-Stahl Experiment and DNA Replication

The Meselson-Stahl experiment tested the hypotheses of DNA replication. They cultured bacteria in a ¹⁵N medium. ¹⁵N is a heavy isotope of nitrogen, so the synthesized DNA is of heavy density. They then shifted the bacteria to a ¹⁴N medium, and DNA was isolated at different times corresponding to replication cycles 0, 1, and 2.

Results of the Experiment

After one replication cycle, the DNA was all of intermediate density. This rules out the conservative replication model, which predicts that both heavy density DNA and light density DNA will be present, but none of intermediate density will be present. This result is consistent with the semi-conservative replication model, which predicts that all DNA... Continue reading "Meselson-Stahl Experiment: Unraveling DNA Replication" »