Transcript Chapter 1 - Los Angeles City College

Chapter 1
Biology 25: Human
Biology
Prof. Gonsalves
Los Angeles City College
Loosely Based on Mader’s Human Biology,7th edition
Chapter 1
Introduction: The Scientific Study of Life
Biology: The study of life.
Greek origin:
Bio: Life
Logos: Study of
I. Life is based on many structural levels
Levels of biological organization:
– Atoms
– Molecules
– Subcellular organelles
– Cells
– Tissues*
– Organs*
– Organ systems*
– Organism: May consist of a single cell or a
complex multicellular organism.
* Level of organization not found in all organisms
Levels of organization beyond organism:
• Population: Group of organisms of the same species that
interact with one another.
• Community: Several different populations living
together in same area (e.g.: lake, forest, jungle).
• Ecosystem: Interactions of community with non-living
environment (air, water, soil).
• Ecosphere: All ecosystems on planet earth. Includes:
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Biosphere: All biological communities on earth.
Atmosphere (air)
Hydrosphere (water)
Lithosphere (crust)
Common features of all organisms:
1. Cells: Basic structural and functional unit of
life. Genetic information contained in DNA.
2. Growth and Development:
• Growth: Occurs by an increase in cell size, cell
number, or both.
• Development: Changes that take place during an
organism’s life.
3. Energy use and metabolism:
• All organisms must take in and transform energy to
do work, to live.
• Metabolism: All chemical reactions and energy
transformations essential for growth, maintenance,
and reproduction.
4. Regulation
• External environment may change, but internal
environment remains fairly constant.
– Homeostasis: Organisms constantly strive to maintain a
“steady state” (e.g.: constant body temperature or blood pH)
despite changes in the internal and external environment.
– Metabolism is regulated by homeostatic mechanisms.
5. Movement:
• Internal movement: Characteristic of all life.
• Locomotion: Self-propelled movement from point A to
point B. Not observed in all life forms.
6. Respond to environmental stimuli: Organisms
respond to internal and external changes (visual
stimuli, temperature, light, sound, pressure, etc.).
7. Order: Organisms are highly organized,
when compared to nonliving environment.
8. Reproduction: Organisms come from other
organisms. Reproduction may be sexual or
asexual.
9. Evolutionary adaptation: Populations, not
individuals, “evolve” or change over many
generations so they can survive in a changing
world.
Evolution is the core theme of biology
– Charles Darwin: Wrote “On the Origin of
Species by Means of Natural Selection” (1859)
in which he proposed the theory of evolution.
Evidence that led to the principle of evolution:
– Fossils: Most species that ever existed are
extinct; appear to be gradual progression
– Artificial selection of domestic/farm animals
– Adaptations: Organisms appear uniquely
suited to their environment (especially in
Galapagos).
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Darwin’s finches are a classic example
The theory of evolution by natural selection:
1. Genetic Variation: Due to genetic differences
there is variation within a population (size, color,
structure, etc.). These differences can be passed
on to an individual’s offspring.
2. Overproduction: Many more organisms are
born, than those that survive and reproduce.
3. Limits on population Growth: Limited
resources (food, water, space, sunlight, etc.)
creates competition
4. Differential reproduction: Organisms with
features that help them compete will be more
likely to survive and reproduce.
Natural Selection Changes Populations
Theory of evolution by natural
selection:
Consequences of natural selection
Over time, the characteristics of a
population will “evolve” and assume those
features that are “naturally selected”.
What is the heritable molecule with the
blueprints for the traits of an organism?
–DNA: Deoxyribose nucleic acid
All life can be classified taxonomically
– Taxonomy: The branch of biology concerned with
naming and classifying organisms
– Most Biologists Recognize Five Kingdoms: Monera,
Protista, Plantae, Fungi, and Animalia
1. Kingdom Monera (Procaryotae): Most widespread
organisms.
• Procaryotes (“Before nucleus”):
– Lack nuclear membrane around DNA.
– Lack membrane bound organelles (mitochondria, chloroplast,
golgi, endoplasmic reticulum).
• Unicellular: Single celled organisms.
• Have a cell wall.
• Include: Bacteria.
Kingdom Prokaryotae: Bacteria lack
nucleus and membrane bound organelles
Five Kingdoms of Living World:
2. Kingdom Protista:
• Eucaryotes (True nucleus):
– Have nuclear membrane around DNA.
– Have membrane bound organelles (mitochondria,
chloroplast, golgi, endoplasmic reticulum).
• Unicellular or simple multicellular.
• Most are larger and more complex than bacteria.
• Some have cell walls, others don’t.
• Some make their own food (phothosynthetic), others
must eat other organisms.
• Include: Protozoa, algae, slime molds.
Kingdom Protista: Eucaryotic Unicellular or
Simple Multicellular Organisms
Five Kingdoms (Continued):
3. Kingdom Fungi:
• Most are multicellular.
• Eucaryotes:
– Have nuclear membrane around DNA.
– Have membrane bound organelles (mitochondria,
chloroplast, golgi, endoplasmic reticulum).
• Have cell walls.
• Heterotrophs: Obtain food from other organisms.
• Most are decomposers, which absorb food from
dead organisms.
• Include: Mushrooms, yeasts, and molds.
Five Kingdoms (Continued):
4. Kingdom Plantae:
• Complex multicellular organisms.
• Cellulose cell walls.
• Eucaryotes: Have nuclear membrane around DNA
and membrane bound organelles.
• Autotrophs: Convert sunlight, water, and carbon
dioxide into food through photosynthesis.
• Other features:
– Waxy cuticle that prevents water loss.
– Multicellular sex organs.
– Openings in leaves and stems for gas exchange (stomata).
• Include: Trees, flowering plants, and mosses.
Five Kingdoms (Continued):
5. Kingdom Animalia:
• Complex multicellular organisms.
• Lack cell walls.
• Eucaryotes: Have nuclear membrane around DNA
and membrane bound organelles.
• Heterotrophs: Obtain chemical energy from living
sources. Eat other organisms for nourishment.
• Features of complex animals:
– High degree of tissue specialization and body
organization.
– Locomotion.
– Well developed sense organs, nervous system, and
muscles.
• Include: Sponges, worms, insects, and vertebrates.
Interdependence of Biological Groups
1. Producers or Autotrophs:
• Self-nourishing organisms (plants, algae, etc.).
• Produce food from simple raw materials.
• Most carry out photosynthesis:
CO2 + H2O + Sunlight -----> Food + Oxygen
• Depend on nonproducers for carbon dioxide
2. Consumers
• Mainly animals.
• Heterotrophs that obtain food directly or indirectly
from producers.
• Carry out cellular respiration:
Food + Oxygen -----> CO2 + H2O + ENERGY
Gas exchange between producers and consumers helps
maintain balance of life-sustaining gases in atmosphere.
Interdependence of Biological Systems
3. Decomposers:
• Some bacteria, fungi, and animals.
• Recycle nutrients by breaking down products and
bodies of dead organisms.
• Process is vital because makes nutrients available
for use by other organisms.
• All organisms interact with each other and the
environment they live in.
• Interactions between producers, consumers, and
decomposers are essential to maintain proper conditions
for life on earth.
Photosynthesis Helps Counteract the Greenhouse Effect
– The earth’s atmosphere contains about 0.03% of carbon dioxide.
– Carbon dioxide traps solar energy in the atmosphere, making the
earth about 10oC warmer than it would otherwise be.
– Since the mid 1800s, the atmospheric levels of carbon dioxide
have risen steadily due to the burning of fuels and forests.
– The “Greenhouse Effect” refers to the global warming that is
caused by increased atmospheric carbon dioxide levels.
– Global warming may cause polar ice caps to melt, which in turn
could cause massive coastal flooding and other problems.
– Plants use up about half of carbon dioxide generated by humans
and other organisms.
Greenhouse Effect: Heat is Trapped by
Carbon Dioxide
SCIENCE AS A METHOD OF INVESTIGATION
Scientia (Latin): To know
Science is a systematic way of thinking, answering
questions, and solving problems.
Steps of scientific method:
1. Observations
2. Question
3. Hypothesis
4. Predictions
5. Test predictions (Experiments)
Results of experiments may:
– Support (but not prove) hypothesis
– Disprove hypothesis -----> Change hypothesis.
Scientific method (Continued):
Hypothesis:
– Proposed explanation for observations
– An “educated guess”, should be consistent with
established facts
– Capable of being tested, should generate predictions.
– Falsifiable, may be proven false (but not proven true).
Variables in an Experiment
– Dependent Variable: What a scientist measures.
– Independent variable: What a scientist controls or
manipulates.
– Standardized variables: What remains the same
throughout experiment. E.g.: Age, sex, race, nutrition,
health, etc.
Control Treatment:
– Independent variable is eliminated or set at a standard
value.
Levels of Treatment
– Values set for the independent variable.
Scientific method:
Replication
– Experiments are repeated numerous times.
– Consistent results increases confidence in results.
– Sample size: Larger sample sizes are generally better.
Theory:
– Hypothesis supported by a large body of observations and
experiments.
– Good theories relate previously unrelated facts and grow
as new information is obtained.
Principle:
– A theory that over time has yielded true predictions.
– Almost universally accepted.
Law:
– A principle of great basic importance.
– Law of gravity or biogenesis.