This document provides an overview of biology in the 21st century. It discusses how biologists study life in all its forms on Earth, including the incredible diversity of species and organisms. Key topics covered include cells, the need for energy, response to the environment, reproduction, and the characteristics that define life. Unifying themes that apply across all levels of biology like structure-function relationships and homeostasis are also summarized.

1. Biology in the
21 Century
st

2. The Study of Life
Biologists study life in all its forms
Earth is Home to an Incredible Diversity of Life!

3. The Biosphere
 All living
things and all
the places
they are found
on earth

4. Biodiversity
 The variety of life
 Why is biodiversity greater closer to the
equator?
 More living things are able to survive in
consistently warm temperatures than in areas
that have changes in temperature

5. Species
 A particular type of living things that can
reproduce by interbreeding among
themselves
 About 2 million species have been identified,
but biologists estimate that over 10 million
remain to be discovered
 Every year about 10,000 new species are
identified!

6. Organism
Any individual
living thing
All organisms share certain characteristics

7. Characteristics of Life
 Cells
 Need for energy
 Response to environment
 Reproduction and development

8. Cells
 All organisms are
made up of one or
more cells
 A cell is the basic
unit of life

9. Need for Energy
 Energy is the ability to cause a change or
to do work
 The form of energy used by all living
things is chemical energy
 Animals get their energy by eating other
organisms
 Metabolism – the chemical processes that
build up or break down materials

10. Response to Environment
 Light, temperature, and touch are just a
few of the physical factors to which
organisms must respond.
 These factors are called stimuli

11. Reproduction & Development
 Members of a species must have the
ability to produce new individuals.
 In all organisms, the genetic material is
DNA
 The process of development allows
organisms to mature and gain the ability
to reproduce

12. Unifying Themes of Biology

13. All Levels of Life Have
Systems of Related Parts
 A system is an organized group of related
parts that interact to form a whole
 Two organisms that interact can also be a
system

14. Structure & Function are
Related in Biology
 What something does (function) in an
organism is directly related to its shape or
form (structure)
 Example: You bite with your sharp front
teeth and chew with your molars

15. Organisms Must Maintain
Homeostasis to Survive in
Diverse Environments
 While environmental conditions change,
the conditions inside organisms usually
stay stable
 Homeostasis is usually maintained through
negative feedback, a change in a system
causes a response that tends to return
that system to its original state

16. Evolution Explains the
Unity and Diversity of Life
 Evolution is the change in the genetic
makeup of a subgroup of a species over
time
 It occurs through natural selection of
adaptations.

17. Science is a way of thinking,
questioning, and gathering evidence

18. There is no single “scientific method”
but investigations tend to have
common stages:
 Collecting Observations
 Asking Questions
 Forming Hypotheses and Making Predictions
 Confirming Predictions
 Drawing Conclusions
 Viewing Conclusions in Context

19. Observation
 the act of noting or perceiving objects or
events using the senses

20. Forming a Hypothesis
 HYPOTHESIS – an educated guess based
on what is already known
 Must be backed up by fact
 PREDICTION – expected outcome of a
test, assuming the hypothesis is correct

21. EXPERIMENT – a planned
procedure to test a hypothesis
 CONTROL GROUP – a group in an experiment
that receives no experimental treatment
 EXPERIMENTAL GROUP – a group that receives
experimental treatment
Control and experimental groups are identical
except for one variable!

22. Variables in an Experiment
INDEPENDENT DEPENDENT
VARIABLE – the VARIABLE – the
one factor that variable that is
is changed in an measured as a
experiment result of the
change in the
independent
variable

23. Drawing Conclusions
• Once data are collected and analyzed, a
conclusion is made as to whether the data
support the hypothesis.
• The hypothesis may be supported or rejected.
• A hypothesis can be supported, but never
proven because another experiment with new
data and new information may alter the
conclusion.
• Many experiments must be performed in order
for a hypothesis to be proven correct.