bio diversity of living things Flashcards
Random cell facts
The average human being is composed of around
100 trillion individual cells
It would take as many as 50 cells to cover the
area of a dot on the letter “i”
Spontaneous generation
people believed that animals
could come from non-living sources. They thought:
○ Frogs developed from falling raindrops
○ Mice and snakes came from hay and grain
○ Flies and maggots came from rotting meat
These ideas were followed because people
accepted what they were told
The cell theory
In 1838 a German Botanist (Matthias Schleiden) concluded that all plant parts are made of cells
In 1839 a German Physiologist (Theodor Schwann)
stated that all animal tissues are composed of cells
In 1858 a German Physician (Rudolf Virchow) concluded that all cells must arise from
preexisting cells
Discovery of cells
In 1665, English Scientist Robert Hooke discovered
cells while looking at a thin slice of cork
He described the cells as tiny boxes or a honeycomb
He thought that cells only existed in plants and fungi
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In 1673 Anton Van Leeuwenhoek used a handmade microscope to observe pond scum
He discovered single-celled organisms that he called
animalcules
He also saw blood cells from fish, birds, frogs, dogs,
and humans
This was the first evidence that cells could be found
in animals and plants
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After the Hooke and Leeuwenhoek discoveries very little advancements were
made
In the mid 1600s Francesco Redi (an Italian doctor and poet) designed a control
experiment
It took hundreds of years of experiments to convince people that spontaneous generation does not occur
He put dead snakes, eels, and veal in large wide mouthed vessels. He sealed one set with wax and left the other set
open. Decaying meat had maggots whereas the sealed
meat had no maggots. Wax
sealed vessels did not produce maggots because
flies were unable to reach the meat.
Redi’s critics said his closed jars had a lack of air, and since everything needs air no flies were able to grow. They did not believe that he proved anything.
He used mesh instead of wax to seal the jars. This allowed
air in but not flies. He found that flies laid eggs on top of the mesh (there were no maggots in the meat)
Reid concluded that all living beings come from seeds of the plants or animals themselves
In 1859 Louis Pasteur (a French chemist) entered a
contest sponsored by the French Academy of Sciences to prove or disprove Spontaneous Generation
He used swan-neck flasks that allowed air in but trapped dust and microbes
This showed that no growth occurred even after many days
He squashed the idea of Spontaneous Generation completely!
From here the next question arose: how did life on this planet start in the first place?
multicellular
made of many cells such as plants and animals
The ORIGINAL cell theory
The 3 basic components of the original Cell Theory were now complete:
1) All organisms are composed of one or more cells
2) The cell is the basic unit of life in all living things
3) All cells are produced by the division of preexisting cells
Cladistics
Cladistics is a branch of biology that determines the
evolutionary relationships between organisms based on
shared derived similarities
unicellular
made of one cell such as bacteria or amoebas
The MODERN cell theory
Today the Cell Theory contains 4 statements that build on the original Cell Theory.
1) The cell contains hereditary information(DNA) which is
passed on from cell to cell during cell division.
2) All cells are basically the same in chemical composition
and metabolic activities.
3) All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc)
4) Cell activity depends on the activities of subcellular structures within the cell (organelles, nucleus, membrane)
The Cell Theory is now used for disease, health, and
medical research and cures (AIDS, Cancer, Vaccines,
Clothing, Stem Cell Research, etc.)
The Cell
A cell is a basic unit of living things
What types of activities characterize a living being?
* Metabolism (take in nutrition and eliminate waste)
* Growth
* Reproduction
* Movement
* Response to external stimuli
* Adaptation
Living organisms are either unicellular (made of one cell such as bacteria or amoebas) OR
multicellular (made of many cells such as plants and animals)
● Two main types of cells have been discovered:
1. Prokaryotic Cells: before nucleus
2. Eukaryotic Cells: true nucleus
Both Prokaryotic and Eukaryotic Cells:
→ Contain all four biomolecules (lipids, carbs,
proteins, nucleic acids)
→ Have ribosomes and DNA
→ Have a similar metabolism
→ Can be unicellular
→ Have cell and plasma
membranes or a cell wall
Prokaryotic Cells
before nucleus
- Ancient, primitive cell
- No nucleus
- No membrane bound
organelles (just ribosomes) - All are unicellular
- Smaller and more simple
than Eukaryotic Cells - DNA is single stranded and circular
Example: all bacteria
Prokaryotes are single-celled organisms
● Prokaryotic microbes belong to the kingdoms
bacteria and archaea
There are three common shapes of prokaryotic microbes:
○ Spherical (cocci)
○ Rod-like (bacilli)
○ Spiral (spirilla)
Examples of bacteria:
-Gram positive
-Cyanobacteria
-Proteobacteria
-Spirochete
-Chlamydia
Archaea
Archaea were first discovered in environments with extremely harsh living conditions
● They are now grouped based on the three types
of extreme conditions in which they are found:
1)Halophiles: salt lovers (areas of high salt)
2)Thermophiles: heat lovers (areas of hot water)
3)Methanogens: lack oxygen (ie. landfills)
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Prokaryote reproduction
All prokaryotes reproduce asexually
→ This means making identical offspring from one parent cell
● There are different ways asexual reproduction can occur
Prokaryotic cells reproduce using binary fission: one cell splits into two identical cells
Phylogenic species concept
Phylogeny (the history of the evolution of organisms) is
used to identify species
● Phylogenies are determined on the basis of developmental, structural and molecular traits
● Relationships are shown in a branching diagram called a phylogenetic tree
Phylogenic tree: Like a family tree, the roots or base of the
phylogenetic tree represent the oldest ancestral species
The upper ends of the branches represent present
day species
Forks in each branch represents the points in the
past at which an ancestral species split (evolved or
changed overtime) becoming two new species
Eukaryotic Cells
true nucleus
- Evolved from a prokaryotic-like predecessor
- Have a nucleus and nuclear envelope
- Bigger and more complex than prokaryotes
- Have membrane bound organelles
- DNA is double stranded and forms chromosomes
- Can be uni OR multicellular organisms
Example: animals, plants, fungi
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Eukaryotes are complex organisms
● These organisms contain cells with organelles and nuclear membranes
● Eukaryotic organisms belong to the kingdoms
protista, fungi, plantae, and animalia
Classifying organisms
Greek philosopher Aristotle (4th century BC) began by
classifying all things into three categories:
■ Animal
■ Vegetable
■ Mineral
He grouped animals according to habitat (land, water, air)
○ 17th century Englishman John Ray first used the term
species while attempting to catalogue all organisms
Carolus Linnaeus (18th century Swedish naturalist) classified all then-known organisms into two large groups: Plantae and Animalia
● He grouped organisms into these two groups according to similarities of physical and structural features
● The groups to which Linnaeus assigned organisms are called taxa (singular: taxon)
● The science of naming organisms and assigning them to these groups is called taxonomy
Common ancestor
If two species share the same evolutionary history it means they have a fairly recent common ancestor
RECALL: we get our evidence of evolutionary relationships by:
→ looking at the fossil record
→ examining anatomy (ie. homologous structures)
→ examining physiology including internal processes
→ looking at DNA evidence
Evidence shows that in some way all organisms on Earth are genetically related
