Notes, abstracts, papers, exams and problems of Biology

Redi's Experiment
1668, Francesco Redi demonstrated that the maggots found in rotting meat came from fly’s eggs
1.     Redi placed pieces of meat in the same jars
2.     The first he left open, the second one he covered with some fabric and the third he covered with a cork
3.     The three jars were left in the same place and after a few days he saw that there were maggots in the first two jars but not the third one

Pasteur’s Experiment
Louis Pasteur demonstrated that microorganisms were not created from spontaneous generation.
1.     Pasteur placed meat soup in two flasks and bent their neck into an S-shape
2.     He sterilised the liquid by heating it and after two weeks saw that it didn’t decompose
3.     He

Hyperadrenalism:

3-carbon dioxide concentration

Cell Theory

Cells are the basic unit of life, all organisms are made up of 1 or more cells, and all cells arise from existing cells.

Contributors to Cell Theory

Hooke

Robert Hooke, a British scientist, first named cells in 1665. He observed cork with a microscope.

Scheiden

Matthias Jakob Schleiden, a German botanist, concluded that plants were made of cells.

Schwann

Theodor Schwann, a German zoologist, found that all living things are made of cells.

Leeuwenhoek

Antonie van Leeuwenhoek, a Dutch fabric store owner, ground a lens that magnified the microscope 200x's.

Virchow

Rudolf Virchow, a German doctor, disputed the idea of spontaneous generation (the idea that cells come from nothing) and concluded that cells come from other cells.

Cell Structures

Cell

Food and Nutrients

Food is our primary source of nutrients. But what are nutrients exactly?

Nutrients: The Essentials for Life

NUTRIENTS are biomolecules that our bodies need to sustain vital functions. They are the chemical components of food, acting as the building blocks and energy sources our cells need to survive.

Why We Need Nutrients

Cells require nutrients to fulfill three fundamental requirements:

1. Energetic: Certain nutrients, like lipids and carbohydrates, are broken down in our mitochondria to release energy. This energy powers essential functions such as movement, temperature regulation, and more.
2. Structural: Some nutrients, including proteins, lipids, and mineral salts, serve as the building blocks for various body structures. These structures

Life Processes

Life processes are the processes that are necessary for an organism to stay alive. Examples include nutrition and respiration.

Criteria of Life

• Growth
• Movement

Nutrition

Nutrition is the process in which an organism takes in food, utilizes it to get energy for growth, repair, maintenance, etc., and excretes the waste materials from the body.

Types of Nutrition

1. Autotrophic Nutrition

(Auto = self; trophos = nourishment) Examples: Plants, Algae, Blue-green bacteria.

• Process: Photosynthesis (Photo = light; Synthesis = to combine)
• Raw Materials:
  • Carbon dioxide
  • Water
• Energy Conversion: Light/Solar energy to Chemical energy
• Role of Chlorophyll: To trap the sun's energy for photosynthesis
• Factors for Autotrophic Nutrition:
  • Carbon dioxide
  • Water
  • Light
  • Temperature
• Events/

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" »

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" »

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" »

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