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Chapter 1

BIOA01H3 Chapter Notes - Chapter 1: Eukaryote, American Black Bear, Carnivora

Biological Sciences
Course Code
Mark Fitzpatrick

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Chapter 1: Studying Life
1.1 What is Biology
x Biology is the scientific study of living things
x Most living organisms:
o Consist of organized cells
o Contain genetic information
o Use genetic information to reproduce, grow and develop
o Convert and use energy from the environment
o Adapt to environmental change
o Maintain homeostasis
x Some organisms are unicellular (one-celled) while others are multicellular
x Antony van Leeuwenhoek discovered single-celled organisms, and Robert Hooke concluded
that plant tissues were made up of repeated units called cells
x Matthew Schleiden and Theodor Schwann stated the cell theory:
o Cells are the basic structural and physiological units of all living organisms
o Cells are both distinct entities and building blocks of more complex organisms
x Spontaneous Generation t an old doctrine that life emerged from self-assembly of non-
living things (such as maggots from dead meat)
x Louis Pasteur disproved this t life must be present in order for new life to form
x The new cell theory (including the aforementioned statements):
o All cells come from pre-existing cells
o All cells are similar in chemical composition
o Most of the chemical reactions of life occur within cells
o Complete sets of genetic information are replicated and passed on during cell
x Evolution t any genetic or resulting phenotypical change from generation to generation
x Natural Selection t is the process by which heritable traits that make it more likely for an
organism to survive and successfully reproduce become more common in a population over
successive generations
x Species t the group of organisms which have similar looks and can breed successfully with
one another
x Adaptations t traits that enhance the organism`s chance of survival and reproduction in its
x All cells contain genetic information in the genome (combination of all the DNA units)
x DNA molecules are long sequences of four different subunits called nucleotides
x Specific segments of DNA called genes contain the information the cell uses to make
x Proteins Zu}u}oµoZulµuµZ}(v}Pv]u[µµvZ
molecules that govern the chemical reactions within cells
x Different types of cells in an organism must express different parts of their genome
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x Living things acquire nutrients from the environment and harness energy for use in
synthesis and regulation
x Via various processes and chemicals, the living organism maintains its internal environment
at optimal conditions for chemical processes to take place efficiently
x Hierarchy of structural levels in biological organization:
o Atom t smallest unit of matter containing protons, electrons, and neutrons
o Element t pure chemical substance containing only one kind of atom
o Molecule t a chemical substance containing two or more atoms in a certain ratio
o Organelle t specialized subunit within the cell with a specific function
o Cell t working components of living organisms
o Tissue t a group of cells with similar and coordinated functions
o Organs t combine several tissues that function together
o Organ Systems t collaboration of organs to form a regulatory mechanism that
o Organism t recognizable self-contained individual
o Population t a group of many organisms of the same species
o Communities t consist of populations of many species
o Ecosystem t biological communities in the same geographical location
o Biosphere t all the ecosystems on Earth
x Organisms interact in many ways: territorial (defend, and solitary) or cooperation (share and
x Organisms of different species may compete for the same food supply, resulting in natural
selection for specialized adaptations that allow certain individuals to attain food more
x Model systems t systems that were generalized to most, if not all, living things
1.2 How is Life on Earth Related?
x Species on Earth share a common ancestor
x Fossil Record t the preserved remains of organisms that lived in the distant past
x Inference of evolutionary relationships were done via the comparison of anatomical
similarities and differences between two remains
x Life arose 4 billion years ago
x Biologists postulate that complex biological molecules first arose through the random
physical association of chemicals in the environment
x The critical step, however, for the evolution of life had to be the appearance of molecules
that could reproduce themselves and also serve as templates for the synthesis of larger,
stable molecules
x The second critical step was the development of membranes t which kept biological
molecules close together and increased the frequency at which they interacted
x The critical ingredient t fat like molecules that formed spherical vesicles
x This natural process of membrane formation marked the beginning of biological evolution as
cells could replicate
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