1. Chapter 1
Exploring Life

2. The phenomenon we call life
Defies a simple, one-sentence definition
Figure 1.1

3. Overview
Biology
Is the scientific study of life
What are some properties that all living things have in common?
Made of cells
Display order/organization
Utilize energy
Reproduction
Growth and development
Maintain homeostasis = regulation thru adjustments
Respond to the environment
Adapt to their environment = evolve

4. A Closer Look at Cells The cell
Is the lowest level of organization that can perform all activities required for life
25 µm
Figure 1.5

5. All cells share certain characteristics
Two Main Forms of Cells
All cells share certain characteristics
They are all enclosed by a membrane
They all use DNA as genetic information
There are two main forms of cells
Eukaryotic
Prokaryotic

6. Nucleus (contains DNA)
Two Main Forms of Cells
Prokaryotic cells
Lack the kinds of membrane-enclosed organelles found in eukaryotic cells
EUKARYOTIC CELL
Membrane
Cytoplasm
Organelles
Nucleus (contains DNA)
1 µm
PROKARYOTIC CELL
DNA
(no nucleus)
Eukaryotic cells
Are subdivided by internal membranes into various membrane-enclosed organelles

7. Living things are organized
Concept 1.1: Biologists explore life from the microscopic to the global scale
The study of life
Extends from the microscope scale of molecules and cells to the global scale of the entire living planet
The hierarchy of life
Extends through many levels of biological organization:

8. …another example of organization
Order comes from DNA / RNA which stores information about organism
This genetic information can be copied & transmitted from cell to cell, and to next generation
Also has the ability to change (mutation)

9. The molecular structure of DNA
Accounts for it information-rich nature
DNA
Cell
Nucleotide A C T G
(b) Single strand of DNA. These geometric shapes and letters are simple symbols for the nucleotides in a small section of one chain of a DNA molecule Genetic information is encoded in specific sequences of the four types of nucleotides (their names are abbreviated here as A, T, C, and G).
(a) DNA double helix. This model shows each atom in a segment of DNA.Made up of two long chains of building blocks called nucleotides, a DNA molecule takes the three-dimensional form of a double helix.
Figure 1.7
Nucleus

10. Living things are highly organized
Biological systems are much more than the sum of their parts
A system is a combination of components that form a more complex organization
The Emergent Properties of Systems
Due to increasing complexity, new properties emerge with each step upward in the hierarchy of biological order

11. For study purposes, organization must be examined
Reductionism
Involves reducing complex systems to simpler components that are more manageable to study

12. The study of DNA structure, an example of reductionism
Organization
The study of DNA structure, an example of reductionism
Has led to further study of heredity, such as the Human Genome Project
Figure 1.9

13. Living things utilize energy
Plants obtain energy from sun and store it (sugars, carbohydrates) = autotrophic
Animals must eat other living things (heterotrophic)
Food forms building blocks for growth, as well as fuel
Organisms often convert energy into movement as well as for staying alive

14. Living things arise through reproduction
Key: pass on information (genes) from one generation to next
Reproduction involves copying (replication) of DNA
Information in DNA codes for structures as well as processes (metabolism) within cell
Often also involves sex- each parent contributes half offspring’s DNA. Offspring differs from both parents
Some reproduce without a mate (asexually). Make new individual by duplicating own DNA. Offspring identical to parent (clones).

15. Living Things Grow and Develop
Most start small and increase in size, and/or in numbers of cells, over their lives
Large organisms start as single cell (zygote), that divides millions of times to form baby
Cells divide many more times in a lifetime
Some cell division results in growth, but some goes to repair and maintenance
E.g. replacement of skin and hair
Egg cell
Sperm cell
Nuclei
containing
DNA
Fertilized egg
with DNA from
both parents
Embyro’s cells with copies of inherited DNA
Offspring with traits
inherited from
Figure 1.6

16. Living things are Homeostatic
To survive, must maintain tolerable (relatively constant) internal environment
Much of energy acquired is used to maintain homeostasis
When balance is disturbed, organisms get sick or die
Temperature pH
etc

17. Feedback Regulation in Biological Systems
A kind of supply-and-demand economy
Applies to some of the dynamics of biological systems
In feedback regulation
The output, or product, of a process regulates that very process

18. In positive feedback The end product speeds up production W Enzyme 4X Y Z
Enzyme 4
Enzyme 5
Enzyme 6
Positive feedback
Figure 1.12

19. Living things Respond to Stimuli
Detect and respond to information about environment
Plants turn leaves to sun; grow roots toward water
Animals move toward food, away from predators or toward own species
Organism’s responses form basis of “behavior”
Usually focused on procuring food, finding mates and avoiding injuries (self-preservation)

20. Living things are adapted, have evolved:
All living things are exquisitely suited to their habitats and the roles they play within them
Adaptations reflect evolutionary history in which environment shaped species
Each individual has different DNA
Some are more successful than others
More successful organisms pass on more genes so successful traits increase until most have successful adaptations
Genetic similarities: Organisms share some basic traits because they descended from same original cell (common ancestry)
Genetic differences: Organisms are different because they’ve adapted to different habitats