Chapter 1 | Biology: The Science of Life

1.1 The Characteristics of Life

• Biology
  • The scientific study of life
• Biologists study life diversity and characteristics shared by all living organisms; such characteristics include the following:
  • Levels of organization
  • The ability to acquire materials and energy
  • The ability to maintain an internal environment
  • The ability to respond to stimuli
  • The ability to reproduce & develop
  • The ability to adapt and evolve to changing conditions.
• By studying biology, we gain insight into the complex nature of life, which allows us to distinguish non-living things from living organisms.
• The complex organization of life begins with atoms
• Atoms
  • The basic units of matter
• Atoms combine to form small molecules, which then join to form larger molecules within a given cell.
• A cell is the smallest, most basic unit of life.
  • Although a cell is considered to be “alive,” it, in fact, is made from nonliving molecules.
• The majority of life on the planet, such as bacteria, are single-celled, while plants, fungi, and animals are multicellular organisms which also means they are composed of many types of cells which combine to make tissues.
• Tissues combine to form organs.
• Organs work together in organ systems.
  • Example: The heart and blood vessels form the cardiovascular system.
  • Various organ systems often work together within complex organisms.
• The organization of life extends beyond the individual organism.
• Species
  • A group of similar organisms that are capable of interbreeding.
  • All members of a given species within a particular area belong to a population.
• Communities form when populations such as humans, zebras, and trees interact.
• On an ecosystem level, communities interact within a physical environment (soil, atmosphere, etc.).
• Biosphere
  • The name given to the collected ecosystems on the planet
  • The zone which air, land, and water at the surface of the earth where living organisms are found.

Life Requires Materials and Energy

• The sun is the ultimate source of energy for nearly all life on earth.
• Plants and certain other organisms are able to capture solar energy and carry photosynthesis.
• Photosynthesis
  • A process that t ransforms solar energy into the chemical energy of nutrition molecules.
  • Organisms that use photosynthesis are often called producers.
• Both plants and animals achieve energy by metabolizing or breaking down the nutrition molecules made by the producers.
• The energy and chemical flow between organisms also defines how an ecosystem functions.
• The process of chemical cycling and energy flow begins when producers, such as grasses, take in solar energy and inorganic nutrients to produce food (organic nutrients) by photosynthesis.
  • Chemical cycling occurs as chemicals move from one population to another in a food chain until death and decomposition allow inorganic nutrients to be returned to the producers.
  • Energy flows from the sun through plants and other members of the food chain as they feed on one another.
  • The energy produced gradually dissipates and returns to the atmosphere as heat; because energy doesn’t cycle, ecosystems could not stay in existence without solar energy and the ability of photosynthetic organisms to absorb it.
• Both energy flow and nutrient cycling in an ecosystem largely determine where different ecosystems are found in the biosphere.
  • On a similar note, the availability of energy and nutrients also determines the type of biological communities that occur within an ecosystem.
• Two of the most biologically diverse ecosystems include tropical rainforests and coral reefs.

Living organisms Maintain an Internal Environment

• For metabolic processes to continue, living organisms need to keep themselves stable in regard to temperature, moisture level, acidity, and as well as many more factors that are vital to maintaining life.
• A significant amount of an organism’s metabolic activities are involved in maintaining homeostasis and or an internal environment that acts within a set of physiological boundaries.
  • Animals often vary their activity to regulate their internal environment.

Living Organisms Respond

• Living organisms find energy/nutrients by interacting with their surroundings.
  • This also applies to single-celled organisms such as bacteria.
• Multicellular organisms have the ability to manage more complex responses
• A proper response from organisms helps ensure their survival and allows them to carry on in their daily activities.

Living Organisms Reproduce and Develop

• Life may only originate from life; every living organism has the ability to reproduce or make another organism like itself.
  • Single-celled organisms simply split in two.
• Reproduction of an organism typically occurs with an egg from one partner and a sperm cell from another; this, inturn, creates an immature individual which grows and develops through various stages to become an adult.
• An embryo develops into a whale or a yellow daffodil, or a human because of the specific set of genes or genetic instructions inherited from its parents.
• In all organisms, the genes are located on long molecules of DNA
• DNA
  • Deoxyribonucleic acid is also known as the genetic blueprint of life.
• The variations of DNA account for the differences between both species and individuals.
• Variations of DNA are a result of mutations or inheritable changes in genetic information.
  • Mutations provide an essential source of variation in genetic information.
  • Mutations are not all bad; examples of this include variations in the eye as well as hair color.
• By studying DNA, scientists are able to understand the basis for specific traits, such as the susceptibilities of specific cancers and the evolutionary history of certain species,
• Reproduction involves the passing of genetic information from a parent to its offspring, and it is because of this that DNA represents a record of our molecular heritage.
  • This is not only limited to just records of a person’s lineage but also how we relate to other species.
• DNA provides the blueprint for the organization and metabolism of the particular organism in question.
  • All the cells in a multicellular organism contain the same set of genes but only specific ones are activated in each type of specialized cell.
• Development
  • The process in which cells express specific genes to distinguish themselves from other cells, which then forms organs and tissues.

Living Organisms Have Adaptations

• Adaptations
  • Modifications that make a species suited to their way of life.

1.2 Evolution: The Core Concept of Biology

• Despite the diversity in form, function, and lifestyle, organisms share the same essential characteristics.

  • Their genes are composed of DNA, and they carry out the
    same metabolic reactions to acquire energy and maintain their organization.
  • The unity of living organisms suggests that they are descended from a common ancestor—the first cell or cells.

  

• An evolutionary tree is like a family tree; similarly, a family tree shows how a group of people has descended from one couple, and an evolutionary tree traces the ancestry of life on Earth to a common ancestor.

  • One couple can have diverse children, and likewise, a population can be a common ancestor to several other groups, each adapted to a particular set of environmental conditions.

• Evolution

  • the process in which populations change over time to adapt to their environment and pass on these changes to the next generation.

• Evolution is considered the unifying concept of biology because it explains so many aspects of biology, including the following:

  • How living organisms arose from a single ancestor
  • The tremendous diversity of life on the planet.

Natural Selection and Evolutionary Processes

• During the nineteenth century, naturalists Charles Darwin and Alfred Russel Wallace came independently to the conclusion that evolution occurs by means of a process called natural selection.
• Charles Darwin
  • famous for writing the book called “On the Origin of Species,” which presented much data to substantiate the occurrence of evolution by natural selection.
• Evolution has become the core concept of biology because the theory explains so many different types of observations in every field of biology.
• Natural selection
  • The mechanism of evolutionary change that is based on how a population changes in response to its environment.
• Environments may change due to the influence of living factors or nonliving factors.
  • Living factor example: New Predators
  • Nonliving factors: Temperature
• As an environment changes over time, some individual species may possess particular adaptations that make them better suited to the new environment.
  • Species that are better adapted to their environment tend to live longer and produce more offspring than other individuals.
• The natural selection process results in changes in the characteristics of a population over time; that being that adaptation that results in higher reproductive success tends to increase in frequency in a population from one generation to the next.
  • The change in the frequency of traits in populations is called evolution.
• The study of evolution encompasses all levels of biological organization.
  • Much of today’s evolution research is carried out at the molecular level, comparing the DNA of different groups of organisms to determine how they are related.
• Studying evolution by natural selection also has practical applications, including the prevention and treatment of disease.
• Bacteria can survive antibiotic drugs in many different ways.
  • For example, certain bacteria can endure treatment with penicillin because they break down the drug, rendering it harmless.
  • If even one bacterial cell lives because it is antibiotic-resistant, then its descendants will inherit this drug-defeating ability.
  • The more antibiotic drugs are used, the more natural selection favors resistant bacteria, and the more often antibiotic-resistant infections will occur.

Organizing the Diversity of Life

• There are two areas of biology that help us group organisms into categories, those being Taxonomy & systematics.
• Taxonomy
  • The discipline of identifying and naming organisms according to certain rules.
• Systematics
  • The discipline that makes sense out of the variety of life on Earth by classifying organisms according to their presumed evolutionary relationships.

Categories of Classification

• The classification categories, from least inclusive to most inclusive include the following:
  • Species
  • Genus
  • Family
  • Order
  • Class
  • Phylum
  • Kingdom
  • Domain

Domains

• Biochemical evidence suggests that there are only three domains of life, those being the following:
  • Domain Bacteria
  • Domain Archaea
  • Domain Eukarya
• Both domain Archaea and domain Bacteria contain prokaryotes.
  • Prokaryotes are single-celled, and they lack the membrane-bound nucleus found in the eukaryotes of the domain Eukarya.
• Prokaryotes are structurally simple but metabolically complex.
• Archaea live in aquatic environments that lack oxygen or are too salty, too hot, or too acidic for most other organisms.
• Bacteria are found almost everywhere; in the water, soil, and atmosphere, as well as on our skin and in our mouths and large intestines.
  • Although some bacteria cause diseases, others perform valuable services, both environmental and commercial.
  • For example, they are used to purify water in our sewage treatment plants.

Kingdoms

• As it stands, there are four kingdoms within the domain of Eukarya, those being the following:
  • Protists
  • (kingdom Protista) are a very diverse group of eukaryotic organisms, some of which are single-celled and others multicellular.
  • Fungi
  • (kingdom Fungi) are the familiar molds and mushrooms that, along with many types of bacteria, help decompose dead organisms.
  • Plants
  • (kingdom Plantae) are well-known as multicellular photosynthesizers.
  • Animals
  • (kingdom Animalia) are multicellular organisms
    that ingest their food.

Scientific Naming

• Religion, aesthetics, ethics, and science are all ways that humans have to find order in the natural world.
• Science differs from other disciplines by its process, which often involves the use of the scientific method.
  • The scientific method acts as a guideline for
    scientific studies.
  • Scientists often modify or adapt the process to suit their particular area of study.

1.3 Science: A Way of Knowing

Start with an Observation

• Scientists believe that nature is orderly and measurable, That natural laws such as the law of gravity do not change with time, and that natural events or “phenomena” can be understood more thoroughly through observations.

  

• Observation

  • A formal way of watching the natural world.

• Scientists rely on their senses to make observations, including sight, hearing, and touch.

  • Scientists will often use tools to enhance their senses, things as microscopes.

• Scientists often expand their understanding by taking advantage of the knowledge and experiences of other scientists, including looking at previous studies or engaging with other scientists who are researching similar topics.

Develop a Hypothesis

• After making an observation(s) and gathering information about a phenomenon, scientists will then use inductive reasoning.
• Inductive reasoning
  • The use of creative thinking to combine isolated facts into a cohesive whole.
• Hypothesis
  • A possible explanation for an event.
• A hypothesis is based on existing knowledge, so it is much more informed than a mere guess.
• A hypothesis, in most cases, is not supported and must be either modified and subjected to additional study or rejected.
• Moral and religious beliefs, while very important to our lives, differ among cultures and through time and are not always testable.

Make a Prediction and Perform Experiments

• Experiment
  • A series of procedures designed to test a specific hypothesis.
• Experimental design
  • The manner in which a scientist intends to conduct an experiment.
• An excellent experimental design ensures that scientists are testing what they want to test and that their results will be meaningful.
• If a hypothesis is well-prepared, Scientists should be able to make a prediction of what the results of the experiment will be and If the results of the experiment do not match the prediction, then the scientist must revisit the initial hypothesis and design a new set of experiments.
• Experiments can take many forms, depending on the area of biology that the scientist is examining.
• In all experimental designs, the researcher attempts to keep all of the conditions constant except for an experimental variable.
• Experimental variable
  • The factor in the experiment that is being deliberately changed.
• Responding variable
  • Also known as the dependent variable, it is the variable a scientist predicts will change if the manipulated variable changes.
• Test groups and control groups keep an experiment results meaningful
• Test Group
  • A test group is exposed to the experimental variable.
• Control Group
  • A control group is not exposed to the experimental variable
• If the control group and test groups in an experiment show the same results, the experimenter knows that the hypothesis predicting a difference between them is not supported.
• Scientists often use model systems and model organisms to test a hypothesis.
  • Model organisms are chosen because they allow the researcher to control aspects of the experiment, such as age and genetic background.
  • Although models provide helpful information, they do not always answer the original question completely.
• Biologists, and all other scientists, continuously revise their experiments to understand better how different factors may influence their original observation.

Collect and Analyze the Data

• Data
  • The results of an experiment
• The more significant variation in data, the more there is a probability of error.
• Even if data shows correlation, correlation does not necessarily mean causation.

Develop a Conclusion

• Scientists must analyze collected data in order to reach a conclusion about whether a hypothesis is supported or not.
  • Since science progresses, the conclusion of one experiment can lead to the hypothesis for another experiment.
  • Results that do not support one hypothesis can often help a scientist formulate another hypothesis to be tested.
• Scientists often report their findings in scientific journals so that their methodology and data are available to other scientists.
  • This is often seen as a standard.
• Experiments and observations must be repeatable.
  • In order for an experiment or observation to qualify as being repeatable, it must be easily reproduced by any scientist who attempts the same experiment that was tested and published; otherwise, it lands in question.

Scientific Theory

• The ultimate goal of science is to understand the natural world in terms of scientific theories.
• Scientific theories
  • Accepted explanations for how the world works.
• Some of the fundamental theories of biology include the following:
  • Cell theory
  • Gene theory
  • Theory of evolution
• The theory of evolution is considered the unifying concept of biology because it pertains to many different aspects of organisms.
  • The theory of evolution has helped scientists generate new testable hypotheses.
• So many observations and experiments have supported the theory of evolution for over 150 years that biologists refer to this theory as a principle.
• Principle
  • Sometimes known as “law,” it is a term sometimes used for a theory that is generally accepted by an overwhelming number of scientists.

Publishing the Results

• Scientific studies are customarily published in a scientific journal

  so that all aspects of a study are available to the scientific community.

  • Before information is published in scientific journals, it is typically reviewed by experts, who ensure that the research is credible, accurate, unbiased, and well-executed.
  • Another scientist should be able to read about an experiment in a scientific journal, repeat the experiment in a different location, and get the same (or very similar) results.

• Some articles are rejected for publication by reviewers when they believe there is something questionable about the design of an experiment or the manner in which it was conducted.

  • Rejection is essential in science since it causes researchers to critically review their hypotheses, predictions, and experimental designs so that their next attempt will more adequately address their hypotheses.
  • It is usual for it to take several rounds of revision before research is accepted for publication in a scientific journal.

1.4 Challenges Facing Science

• Technology
  • The application of scientific knowledge to the interests of humans.
• Scientific investigations are the basis for the majority of
  our technological advances.

Biodiversity and Habitat Loss

• Biodiversity
  • the total number and relative abundance of species, the variability of their genes, and the different ecosystems in which they live.
• The biodiversity of our planet has been estimated to be around 8.7 million species (not counting bacteria), and so far, approximately 2.3 million have been identified and named.
• Extinction
  • The disappearance of a species or larger classifi￾cation category.
• It is estimated that presently we are losing hundreds of species every year due to human activities and that as much as 38% of all species.
• The destruction of healthy ecosystems has many unintended effects; for example, we depend on ecosystems for food, medicines, and various raw materials, but our search for these things has led to worsened flooding problems in specific locations, which leads to what was once fertile farmland being undesirable.
• The workings of ecosystems ensure that the environmental conditions of the biosphere are suitable for the continued existence of humans.
  • Several studies show that ecosystems cannot function correctly unless they remain biologically diverse.

Emerging and Reemerging Diseases

• Emerging diseases

  • Diseases that are relatively new to humans, those including the following:
  • Avian influenza (H5N1 and H7N9)
  • Swine flu (H1N1)
  • Severe acute respiratory syndrome (SARS)
  • middle East respiratory syndrome (MERS)

• Emerging diseases can arise in multiple ways, including new and/or increased exposure to animals or insect populations that act as vectors for disease or Changes in human behavior and use of technology.

• Both emerging and reemerging diseases have the potential to cause
  health problems for humans across the globe.

  • Scientists investigate not only the causes of these diseases

  But also their effects on our bodies and the mechanisms by which they are transmitted.

Climate Change

• Climate change

• changes in the normal cycles of the Earth’s climate that may be attributed to human activity.

• Climate change is primarily due to an imbalance in the chemical cycling of the element carbon.

  • Typically, carbon is cycled within an ecosystem; however,

  due to human activities, more carbon dioxide is being released into the atmosphere than is being removed.

• The increase in CO2 is primarily due to the burning of fossil fuels and the destruction of forests to make way for farmland and pasture.

• The amount of carbon dioxide released into the atmosphere today is about twice the amount that remains in the atmosphere.

• The increased amount of carbon dioxide (and other gases) in the atmosphere is causing a rise in temperature called global warming.

  • These gases allow the sun’s rays to pass through, but they absorb and radiate heat back to Earth, a phenomenon called “the greenhouse effect.”

• There is a consensus among scientists from around the globe that climate change and global warming are causing significant changes in many of the Earth’s ecosystems and represent one of the most significant challenges of our time.

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