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Section # 0141

Introduction to Biology

Chapter 1

Figure 1.2

Figure 1.3

Cells and Their DNA

• The cell is the lowest level of structure that can perform all activities required for life.

– All organisms are composed of cells.

• We can distinguish two major types of cells:

– Prokaryotic

– Eukaryotic

• The prokaryotic cell is simple, small, and contains no organelles.

• The eukaryotic cell is larger and more complex and contains organelles.

– The nucleus is the largest organelle in most eukaryotic cells.

Figure 1.5

• All cells use DNA as the chemical material of genes.

– Genes are the units of inheritance that transmit information from parents to offspring.

• The language of DNA contains just four letters:

– A, G, C, T

Figure 1.6

Discovery Science

• Draw conclusions by observing natural phenomena.

– This limits the scope of science to the study of structures and processes that we can observe and measure.

Figure 1.17

Hypothesis-Driven Science

• Modern scientific investigations and experiments

– The key element of the scientific method is hypothesis-driven science.

Figure 1.18

Figure 1.19

Figure 1.20

The Process of Science: Can Colors Protect a Snake?

• Biologists developed a hypothesis regarding mimicry in snakes: The king snake’s resemblance to the coral snake repels predators

• Prediction: Predators will attack snakes with bright rings of red, yellow and black less frequently than other snakes

– They tested the hypothesis by making artificial snakes and observing how often they were attacked by predators.

Figure 1.21

The results support the hypothesis.

The Culture of Science

• Scientists build on what has been learned from earlier research.

– They pay close attention to contemporary scientists working on the same problem.

– Results should be repeatable

Chemistry for Biology

Chapter 2

Matter: Elements and Compounds

• Matter is anything that occupies space and has mass.

• Matter is found on the Earth in three physical states:

– Solid

– Liquid

– Gas

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Atom - An atom is the smallest unit of matter that still retains the properties of an element.

Table 2.1

Isotopes - alternate mass forms of an element. They have the same number of protons and electrons, but they have a different number of neutrons.

• In radioactive isotopes,

– The nucleus decays, giving off particles and energy.

• Radioactive isotopes have many uses in research and medicine.

– Example: locating biologically important molecules within organisms

Figure 2.7

Chemical Bonding and Molecules

• Chemical reactions enable atoms to give up or acquire electrons in order to complete their outer shells.

– These interactions usually result in atoms staying close together.

– The atoms are held together by chemical bonds.

Figure 2.8

Ionic Bonds are formed between oppositely charged ions

Figure 2.9

Covalent Bonds are formed when two atoms share one or more pairs of outer-shell electrons.

Unnumbered Figure, p. 26

Water is a compound in which the electrons in its covalent bonds are shared unequally.

Figure 2.10

Unnumbered Figure, p. 27

Water and Life

• Life on Earth began in water and evolved there for 3 billion years.

– Modern life still remains tied to water.

– Your cells are composed of 70%–95% water.

• The abundance of water is a major reason Earth is habitable.

Figure 2.11

Figure 2.12

Cohesion – water molecules stick together as a result of hydrogen bonding

Figure 2.13

Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid.

Hydrogen bonds give water an unusually high surface tension.

Water Moderates Temperature

Because of hydrogen bonding, water has a strong resistance to temperature change.

Water can absorb and store large amounts of heat while only rising a few degrees in temperature

Earth’s water supply causes temperatures to stay within limits that permit life.

Figure 2.14

Evaporative cooling removes heat from the Earth and from organisms.

The Biological Significance of Ice Floating

• When water molecules get cold, they move apart, forming ice.

– A chunk of ice has fewer molecules than an equal volume of liquid water.

Figure 2.15

Figure 2.16

Acids, Bases, and pH

• Acid

– A chemical compound that donates H+ ions to solutions.

• Base

– A compound that accepts H+ ions and removes them from solution.

• To describe the acidity of a solution, we use the pH scale.

Figure 2.17

Figure 2.18