Human Biology

Dr. jassim Mohammed Abdo

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Chapter 1

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.

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:

– 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).

• 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..

• 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.

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

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.

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.