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

Cellular Interaction and Responses

Cellular interaction is the capacity of cells to detect changes in their environment and respond to them correctly.

Types of Cellular Responses

Static Response

In a static response, there is no movement produced. Rather, the cell responds in a different way, for example, by secreting a substance.

Dynamic Response (Taxis)

In a dynamic response, the cell responds by moving. These movements are collectively called taxis (plural: taxa). They are considered:

• Positive: If the cell moves towards the stimulus.
• Negative: If the cell moves away from the stimulus.

Mechanisms of Cellular Movement

Flagellar and Ciliary Movement

This type of movement is produced in cells that have cilia (many tiny structures) or flagella (longer than... Continue reading "Cellular Responses, Movement, and Reproduction Mechanisms" »

The Origin of New Species

The changes that living things experience as time passes lead to the creation of new species. In this long and complex process, there are 4 stages:

1. Production of Evolutionary Changes in Populations

This happens because natural selection favors some individuals and not others. As a consequence, the new populations are different from the original ones, although they still belong to the same species.

2. Genetic Isolation of the New Population

So that a new species can evolve, it is essential that the members of the new population do not reproduce with those of the previous population. In other words, they become independent and stop sharing genetic information with the original population.

3. Gradual Differentiation

After... Continue reading "The Origin of New Species and Human Evolution" »

skeletal system:organ system that includes the bones and the connective tissues that hold the bones together.appendicular skeleton:is the part of your skeleton that is adapted to allow the body to move.axial skeleton:is made up of the bones found in the trunk and head of the body.vertebrae:bones that surround the spinal cord.cartilage:flexible connective tissue that is found between your bones.joint:place where two bones meet.joints classify into:gliding joint(flexibility the wrist and ankle)pivot joint(allows the bones in the neck to move a short distance to left to right)ball-and-socket joint(holds the upper arm and leg to trunk of the body and allows these bones to move in almost any direction)saddle joint(gives bones in the finger the ability... Continue reading "Human Skeletal and Muscular Systems: Anatomy and Function" »

Understanding and Managing Stress

Concept of Stress

Stress, an uneasy experience of pressure, can stem from various sources: yourself, others, and the environment. Modern life's fast pace creates numerous pressures, leading to frequent stressful situations. Effective stress management starts with understanding its sources and how to address them.

Self-Inflicted Stress

Sometimes, we create our own stress. This isn't always negative. Eustress, or positive stress, can produce beneficial results. Its counterpart, distress, is the negative dimension of stress.

Environmentally Caused Stress

External factors can also induce stress. Imagine your crops are ready for harvest, but continuous rain creates worry and helplessness. This stress originates from... Continue reading "Stress Management Techniques" »

The Human Heart: Chambers, Vessels, and Blood Flow

Heart Action: Blood Collection, Pumping, and Valve Function

The right atrium collects blood from the superior and inferior vena cava, and the left atrium collects blood from the pulmonary veins. This blood then flows into the right and left ventricles, which pump the blood into the arteries. The direction of blood flow is controlled by the atrioventricular valves and semilunar valves. When the atria contract, the blood flows through the open atrioventricular valves into the ventricles. At this stage, the semilunar valves are closed, so the ventricles fill with blood. The ventricles then contract, which causes a rise in pressure. This rise in pressure first causes the atrioventricular valves to... Continue reading "Human Circulatory and Immune System Fundamentals" »

Parts of Eukaryotic Cells:

• Animal: cytoskeleton, cilia and flagella, proteasomes, ribosomes, nucleus, centrioles, vacuoles, golgi apparatus, endoplasmic reticulum, mitochondria, lysosomes.
• Plant: ribosomes, cell wall, cytoskeleton, proteasomes, plastids, vacuoles, golgi apparatus, nucleus, endoplasmic reticulum, mitochondria.

Cell Cycle:

All changes that a cell undergoes from its formation until its division into two new cells.

Phases:

• Interphase: The longest phase, cells do not divide. Before the end of this phase, cells duplicate their DNA.
• Mphase: This short phase, the cell reproduces by cellular division. Two new cells are formed. This can occur in 2 processes:

Mitosis:

The process in which the cell nucleus duplicates with the same genetic material.... Continue reading "Parts of Eukaryotic Cells and the Cell Cycle" »

Photosynthesis

Photosynthesis is the fundamental process by which plants manufacture carbohydrates from raw materials using energy from light.

The Process of Photosynthesis

• Green plants take in CO2 through their leaves via diffusion.
• Water is absorbed through the plant's roots by osmosis and transported to the leaves through xylem vessels (moving upwards).
• Chloroplasts containing chlorophyll are responsible for trapping light energy. This energy is used to break up water molecules and then to bond hydrogen and CO2 to form glucose.
• Glucose is usually changed to sucrose for transport around the plant or to starch for storage.
• Oxygen is released as a waste product or used by the plant for respiration.

Factors Limiting Photosynthesis

Three factors can limit... Continue reading "Photosynthesis and Diffusion: Biological Processes Explained" »

Neo-Darwinism and the Synthetic Theory

Neo-Darwinism, also known as the synthetic theory, is a revised version of the theory of natural selection, enriched by contributions from studies made in fields such as genetics, paleontology, and taxonomy after Darwin's time.

Punctuated Equilibrium

Punctuated Equilibrium (Punctualism) suggests that there are certain periods of intense speciation which interrupt, or punctuate, the equilibrium of the normal process of adaptation through natural selection.

Biodiversity and Biological Adaptation

Biodiversity refers to the quantity and variety of organisms that exist or have existed in the past, and the adaptation of organisms to different habitats.

Adaptation is the accumulation of changes in the characteristics... Continue reading "Evolutionary Biology: Neo-Darwinism and Hominid History" »

Extracellular is inactive DNA or RNA surrounded by proteinIntracellular – active inside a host cell/ viral reproductionprotein capsid - Viral nucleic acid presentcapsomere- protects genetic materialretroviruses: ss RNA hepadnaviruses: dsRNA enveloped”- membrane lipid bilayer (host)& proteins (virus)naked-+ viral DNA complex viruses- icosahedral head/ helical tail/ Tail fibers attach to host cellviral replication: the virion attaches host specific/ proteins interact w/ receptors on surface/ if receptor not present= can’t infect. 2. Phages often complex3.active/intracell/ production of new virions/ viral mRNA is required SS DNA ->DS DNA -> mRNA / DS DNA= mRNA (w/polymerase) RNA polymerase” to make mRNA from viral RNA/ SS RNA

Key Concepts in Enzymes, Cellular Respiration, and Genetics

1. Free Energy Curve

In a catalyzed reaction, the enzyme lowers the activation energy required for the reaction, making it proceed more quickly. The free energy curve for the catalyzed reaction is shifted to the left compared to the uncatalyzed reaction.

2. Components in a Chemical Reaction

• Reactants: A and B
• Products: C and D (catalyzed)

3. Factors Affecting Enzyme Function

• Temperature: Enzymes have an optimal temperature; deviation can denature them.
• pH: Enzymes function best within a specific pH range.
• Substrate Concentration: Up to a point, increasing substrate concentration increases enzyme activity.

4. Definition of an Enzyme

Enzymes are biological catalysts that accelerate chemical reactions... Continue reading "Enzymes, Cellular Respiration, and Genetics: Key Concepts" »