Download Early History of Earth

Early History of Earth
What was early Earth like?
 Some scientists suggest
that it was probably very
hot.
 The energy from colliding
meteorites could have
heated its surface, while
both the compression of
minerals and the decay of
radioactive materials heated
its interior.
Early History of Earth

Volcanoes might have
frequently spewed lava
and gases, relieving
some of the pressure
in Earth’s hot interior.
These gases helped
form Earth’s early
atmosphere.
The Origin of Life – Early Ideas
 In the past, the ideas that decaying meat produced maggots, mud
produced fishes, and grain produced mice were reasonable
explanations for what people observed occurring in their
environment.
 Such observations led people to believe in spontaneous
generation — the idea that nonliving material can produce life.
 In 1668, an Italian physician, Francesco Redi, disproved a
commonly held belief at the time—the idea that decaying meat
produced maggots (immature flies).
Control group
• Redi’s well-designed, controlled
experiment successfully convinced
many scientists that maggots, and
probably most large organisms, did Experimental group
not arise by spontaneous
generation.
Time
Time
The Origin of Life – Early Ideas

However, during Redi’s time, scientists began to use the latest
tool in biology—the microscope (invented by Anton Van
Leeuwenhoek )

Although Redi had disproved the spontaneous generation of large
organisms, many scientists thought that microorganisms were so
numerous and widespread that they must arise spontaneouslyprobably from a vital force in the air.

In the mid-1800s, Louis Pasteur designed an experiment that
disproved the spontaneous generation of microorganisms.

Pasteur set up an experiment in which air, but no
microorganisms, was allowed to contact a broth that contained
nutrients.

Pasteur’s experiment showed that microorganisms do not simply
arise in broth, even in the presence of air.

From that time on, biogenesis, the idea that living organisms
come only from other living organisms, became a cornerstone of
biology.
Pasteur’s Experiment
Each of Pasteur’s
broth-filled flasks was
boiled to kill all
microorganisms.
The flask’s S-shaped
neck allowed air to
enter, but prevented
microorganisms from
entering the flask.
Microorganisms
soon grew in the
broth, showing that
they come from
other
microorganisms.
Pasteur tilted a flask,
allowing the
microorganisms to enter
the broth.
The Evolution of Cells

Fossils indicate that by about 3.4 billion years ago, photosynthetic
prokaryotic cells existed on Earth. But these were probably not the
earliest cells. The first forms of life may have been prokaryotic
forms that evolved from a “protocell”.

Because Earth’s atmosphere lacked oxygen, scientists have
proposed that these organisms were most likely anaerobic.
• For food, the first prokaryotes
probably used some of the organic
molecules that were abundant in
Earth’s early oceans.
• Over time, these heterotrophs would
have used up the food supply.
• Heterotrophs are organisms which
obtain their food from other
heterotrophs or autotrophs (plants).
The First True Cells

Autotrophs are organisms that can make their own food (i.e.
plants). These first autotrophs were probably similar to present-day
archaebacteria.
• Archaebacteria are prokaryotic
and live in harsh environments,
such as deep-sea vents and hot
springs.
•The earliest autotrophs probably
made glucose by chemosynthesis
rather than by photosynthesis.
•In chemosynthesis, autotrophs
release the energy of inorganic
compounds, such as sulfur
compounds, in their environment
to make their food (they use
chemicals instead of sunlight).
Bill Nye Video Segment – Life
As We Know It
The Endosymbiont Theory (Endosymbiosis)

Complex eukaryotic cells probably evolved from simple
prokaryotic cells.

The endosymbiont theory, proposed by American biologist Lynn
Margulis in the early 1960s, explains how eukaryotic cells may
have arisen.

The endosymbiont theory proposes that eukaryotes evolved
through a symbiotic relationship between ancient prokaryotes.

New evidence from scientific research supports this theory and
has shown that chloroplasts and mitochondria have their own
ribosomes that are similar to the ribosomes in prokaryotes.

In addition, both chloroplasts and mitochondria reproduce
independently of the cells that contain them.

The fact that some modern prokaryotes live in close association
with eukaryotes also supports the theory. (i.e. E.coli in human
gut)
The Discovery of Cells
 Anton Van Leeuwenhoek = Dutch scientist who





invented the first light microscope.
Robert Hooke = English scientist who identified
and named the “cell” while observing cork cells
with a light microscope.
Robert Brown = English scientist who identified
and named the nucleus of the cell.
Matthias Schleiden = German scientist that noted
all plants are made of cells.
Theodor Schwann = German scientist who noted
that all animals are made of cells.
Rudolf Virschow = Russian scientist who stated
that cells come from pre-existing cells.
The Cell Theory
The cell theory (proposed independently in 1838
and 1839) is a cornerstone of biology.
All plants are made of cells.
Schleiden
All animals are made of cells
Schwann
The Cell Theory
1. All organisms are made of one or more cells.
2. The cell is the basic unit of structure and organization of
organisms.
3. All cells come from pre-existing cells.
Modern Additions:
4. All cells contain hereditary information which is passed from cell
to cell during cell division.
5. All cells are basically the same in chemical composition.
6. All energy flow (metabolism and biochemistry) of life occurs
within cells.
Comparing Cells
Two Fundamentally
Different Types of Cells
PROKARYOTES
• All lack a nucleus
• Contain DNA
• Contain cytoplasm
• All lack organelles
• All have a cell membrane
• Only bacteria are made of prokaryotic cells
EUKARYOTES
• All have a nucleus
• All contain organelles
• All contain cytoplasm
• All have a cell membrane
• All contain DNA inside a nucleus
A prokaryotic cell
A eukaryotic cell
“Us vs. Them”
- Eukaryotes
and
Prokaryotes
CELLS!
CELLS!
PROKARYOTE
vs.
EUKAROTE
Common Features
EUKARYOTES
★ Greek = “true nucleus”
★ Compartmentalized with organelles (membrane-bound
structures)
★ Eukaryotic cells include: plant, animal, fungi, protist
EUKARYOTES
PLANT
vs.
Electron Micrograph
ANIMAL
EUKARYOTIC ORGANELLES
PLANT
ANIMAL
★ Cell Wall
★ Centriole
★ Chloroplast
★ Cilia or Flagella
★ Large central vacuole
★ Many small vacuoles
★ Cell/Plasma Membrane
★ Cell/Plasma Membrane
★ Cytoplasm/Cytosol
★ Cytoplasm/Cytosol
★ Mitochondria
★ Mitochondria
★ Ribosomes
★ Ribosomes
★ Nucleus
★ Nucleus
★ Nucleolus
★ Nucleolus
★ Nuclear Envelope/Membrane
★ Nuclear Envelope/Membrane
★ Rough Endoplasmic Reticulum (E.R.)★ Rough Endoplasmic Reticulum
★ Smooth E.R.
★ Smooth E.R.
★ Lysosomes
★ Lysosomes
★ Golgi Body/Apparatus
★ Golgi Body/Apparatus
★ Cytoskeleton
★ Cytoskeleton
Animal vs. Plant Cells – Chloroplasts Are a
Big Part of the Difference
Two Other Unique Features of Plant Cells
The central
vacuole
may occupy
90% of a
plant cell.
EUKARYOTIC ORGANELLES
Structure
Nucleus
Nucleolus
Endoplasmic Reticulum
(Smooth & Rough)
Golgi Apparatus
Lysosomes
Mitochondria
Chloroplasts
(Plant)
Description
Function
EUKARYOTIC ORGANELLES
Structure
Centrioles
(Animal)
Cytoskeleton
Flagella/Cilia
(Animal, fungi and some
protists)
Central Vacuole (Plant)
Cell Wall
(Plant)
Cytoplasm/Cytosol
Ribosomes
Description
Function
EUKARYOTIC ORGANELLES
THE NUCLEUS
★ Latin = “kernel” or “nut”
★ First described by Robert Brown (1831)
★ Most eukaryotic cells contain one central nucleus
★Fungi have many nuclei
★ Contains Nucleolus (where synthesis of ribosomal RNA takes place)
★ Nucleus protected by Nuclear Envelope/Membrane (which
contains nuclear pores)
Structure
Description
Function
Nucleus
Usually spherical surrounded by double
membrane that contains chromosomes
Control center of cell; directs
protein synthesis and cell
reproduction.
Site of genes for ribosomal RNA
(rRNA) synthesis
Assembles ribosomes
Nucleolus
EUKARYOTIC ORGANELLES
THE NUCLEUS
http://www.cartage.org.lb/en/themes/Sciences/Zoo
logy/AnimalPhysiology/Anatomy/AnimalCellStruct
ure/Nucleus/Nucleus.htm
http://www.frontiers-ingenetics.org/en/pictures/nucleus_1.jpg
The Nucleus
Think of the nucleus as the
cell’s control center.
“The
Control
Center of
the Cell”
• Regulates all
cell activity
• Contains
chromatin
composed of
DNA.
Two meters of
human DNA fits
into a nucleus
that’s 0.000005
meters across.
EUKARYOTIC ORGANELLES
THE ENDOPLASMIC RETICULUM
★ Endoplasmic = “within the cytoplasm”
 Reticulum = Latin for “a little net”
 Usually connected to nuclear envelope
★ ROUGH E.R.: Contain many ribosomes, which appear pebbly or
“rough”, and are destined to be exported from the cell;
synthesizes, moves and proofreads proteins.
 SMOOTH E.R.: Relatively few or no ribosomes; may contain
enzymes which can 1) storage and synthesis of lipids and steroids
(testes, intestine, and brain) or; 2) carry out detoxification of
drugs (liver)
Structure
Endoplasmic Reticulum
(Smooth & Rough)
Description
Network of highly folded
phospholipid membranes
within the cytoplasm
Function
Forms compartments and
vesicles; participates in
protein and lipid synthesis;
transports synthesized
proteins
EUKARYOTIC ORGANELLES
THE ENDOPLASMIC RETICULUM
http://www.ccs.k12.in.us/chsBS/kons/kons/eukaryotic%2
0cell/cytoplasm_and_its_associated_str_files/image002.j
pg
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/r
ougher.htm
EUKARYOTIC ORGANELLES
THE GOLGI BODY/APPARATUS
★ Flattened stacks of tubular membranes
★ Smooth, membranous structure located near the middle of the
cell
 Receives proteins and lipids from the E.R.
 Modifies and sorts proteins
 Creates lysosomes
★ Packages proteins into membrane-bound structures, called
vesicles, to be sent to appropriate destinations
★ Similar to a “post office”
Structure
Golgi Body/Apparatus
Description
Flattened stacks of tubular
membranes
Function
Sorts, packages and
transports proteins for
export from the cell
EUKARYOTIC ORGANELLES
THE GOLGI BODY/APPARATUS
http://www.bu.edu/histology/i/20303ooa.jpg
http://media-2.web.britannica.com/eb-media/52/116252004-9615DB80.jpg
EUKARYOTIC ORGANELLES
THE CENTRIOLES
★ Important in animal Cell Division
★ Composed of 9 triplets of microtubules
★ Microtubules = long, hollow cylinders which influence cell shape,
move the chromosomes in cell division, and provide structure for
flagella and cilia
★ Barrel-shaped organelles found in animals and most protists
★ Plants and fungi lack centrioles
★ Occur in pairs, usually at right angles
Structure
Centrioles
Description
Occur in pairs and made of
microtubules; in animal cells
and most protists
Function
Important in cell division,
cell shape and structure for
flagella and cilia
EUKARYOTIC ORGANELLES
CENTRIOLES
http://images.protopage.com/view/721389/3
ydo50yjpdnqy8ag4flqbd1un.jpg
http://upload.wikimedia.org/wikipedia/commons/4/49/Pl
agiomnium_affine_laminazellen.jpeg
EUKARYOTIC ORGANELLES
THE LYSOSOME
★ Membrane-bounded digestive vesicles
★ Arise from the Golgi Apparatus
★ Contain degrading enzymes which break down (recycle) old
organelles
★ Enzymes also function to eliminate harmful or foreign cells
through phagocytosis
 Called “suicide sacs”
 In plants, called peroxisomes
Structure
Lysosome
Description
Vesicles derived from Golgi
apparatus that contain
digestive enzymes
Function
Digests worn-out organelles
and foreign or harmful cells;
acts like a “garbage disposal”;
plays a role in cell death
(“suicide sacs”)
EUKARYOTIC ORGANELLES
THE LYSOSOME
http://www.cartage.org.lb/en/themes/sciences/zoology/A
nimalPhysiology/Anatomy/AnimalCellStructure/Lysosom
es/lysosome.jpg
http://www.stolaf.edu/people/giannini/cell/lys/autophag.j
pg
EUKARYOTIC ORGANELLES
Endocytosis = into the cell
Exocytosis = exiting the cell
The Lysosome
The
Lysosome
This
bacterium is
about to be
eaten by a
white blood
cell and will
spend the
last minutes
of its
existence
within a
lysosome.
EUKARYOTIC ORGANELLES
FLAGELLA/CILIA
★ Made of microtubules
 Aid the cell in locomotion or feeding
 Motion is similar to that of oars in a rowboat
 Flagella are longer projections that move with a whip-like motion
 Cilia are shorter, numerous projections that look like hairs.
 Some protists use a pseudopod (“false foot”) to crawl; similar to
squeezing a water balloon at one end forces the balloon to bulge
out at the other end.
Structure
Flagella/Cilia
Description
Cellular extensions made up
of pairs of microtubules
Function
Aid the cell in locomotion
(movement) or feeding
EUKARYOTIC ORGANELLES
CILIA
FLAGELLA
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
Cilia = tiny
hairs (move
like oars in a
boat)
Flagella =
tails (move
with whip-like
action)
EUKARYOTIC ORGANELLES
THE MITOCHONDRION
★ Plural = Mitochondria
★ Peanut-shaped with outer membrane and highly folded inner
membrane (cristae)
★ Have their own DNA (mitochondrial DNA or mDNA) important
for oxidative metabolism (inherited by you mother)
★ Supply ATP (energy) to the cell; “powerhouse” of the cell
 Similar to a battery, generator or power plant
 Where cellular respiration occurs
★ Cells have many mitochondria (ex: liver cells have up to 2000!)
★ Each time the cell divides, a mitochondrion divides in two
Structure
Mitochondria
Description
Peanut shaped structure
with double membrane
(outer membrane and highly
folded inner membrane
called cristae)
Function
“Powerhouse” of the cell;
sites of oxidative
metabolism
EUKARYOTIC ORGANELLES
MITOCHONDRIA
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/
mito.gif
The Mitochondrion
* Responsible for
Apocytosis =
programmed cell death
* A class of diseases
that causes muscle
weakness and
neurological disorders
are due to
malfunctioning
mitochondria.
Worn out mitochondria may be an important factor in aging.
EUKARYOTIC ORGANELLES
THE CYTOSKELETON
★ Interior framework of the cell
★ Network of protein fibers that support the shape of the cell and
anchor organelles to fixed locations
★ Stretches the plasma membrane like the poles on a circus tent!
★ Allows cells to rapidly alter shape
Structure
Cytoskeleton
Description
Network of protein
filaments
Function
Provides internal structural
support; helps in cell
movement
EUKARYOTIC ORGANELLES
CYTOSKELETON
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
http://www.noble.org/press_release/plantbi
o/blancaflornasa/cytoskeleton.jpg
http://migration.files.wordpress.com/2007
/07/cytoskeleton02.jpg
The Cytoskeleton
The name is
misleading. The
cytoskeleton is the
skeleton of the cell, but
it’s also like the
muscular system, able
to change the shape of
cells in a flash.
An animal cell cytoskeleton
The
Cytoskeleton
in Action
A white
blood cell
using the
cytoskeleton
to “reach
out” for a
hapless
bacterium.
EUKARYOTIC ORGANELLES
THE CHLOROPLAST
★ Greek: chloro = “green”; plasts = “form “ or “entitiy”
★ Commonly in plant cells
★ Contain pigment called chlorophyll (gives plants their green color)
★ Carry out photosynthesis
★ Typically contain one to several hundred
★ Contain two membranes; closed compartment of stacked
membranes called grana which have disk-shaped structures called
thylakoids ; surrounding thylakoid is a fluid matrix called stroma
★ A type of plastid which contains it’s own DNA
Structure
Chloroplast
Description
Flat, disk-shaped green
organelle with two
membranes; contain
chlorophyll, a photosynthetic
pigment
Function
Site of photosynthesis;
produces food for the cell
The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
Only plants have chloroplasts, but animals reap the benefits too.
EUKARYOTIC ORGANELLES
CHLOROPLAST
http://virtualbiologytutor.co.uk/images/chlo
roplast.jpg
http://upload.wikimedia.org/wikipedia/commons/4/49/Pl
agiomnium_affine_laminazellen.jpeg
Cells In a Leaf
A Consequence of Cell
Walls – the Great Strength
of Woody Plants
EUKARYOTIC ORGANELLES
CENTRAL VACUOLE
★ In Plant cells:
 Large sac used to store mainly water and other materials (sugars,
ions and pigments)
 Helps to increase the surface-to-volume ratio by applying pressure
to cell membrane.
 In Animal cells: contain many small vacuoles for temporary storage
Structure
Central Vacuole
Description
In plant cells, large organelle
filled with mainly water, and
other materials; takes up
most of cell
Function
Storage center for water
and other materials; helps
maintain volume of cell
EUKARYOTIC ORGANELLES
CENTRAL VACUOLE
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
Plant Cell
Animal Cell
Animal Cell
VACUOLES
The Central Vacuole Controls Turgor
Pressure
wilts
turgid
EUKARYOTIC ORGANELLES
CELL WALL
★ In Plant and bacterial cells:
 In plants = Composed of fibers made out of cellulose
 In bacteria = composed of peptidoglycan
 Cell walls in plants are thicker and stronger than those in bacteria
(which are primarily made out of protein polysaccharide)
 Made up of a primary and secondary wall
 Also present in fungi and some protists
 Provide protection and support
Structure
Cell Wall
Description
In plant cells, outer layer of
cellulose; in bacteria, outer
layer of protein; also found in
fungi and some protists
Function
Protection and support
EUKARYOTIC ORGANELLES
CELL WALL
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
http://library.thinkquest.org/C0045
35/media/cell_wall.gif
http://www.learner.org/courses/essential/li
fe/images/show2.leaf.jpg
EUKARYOTIC ORGANELLES
CYTOPLASM / CYTOSOL
 Clear, gelatinous fluid that fills the interior of the cell excluding
the nucleus
 Contains sugars, amino acids and proteins that the cell uses to
carry out its everyday activities
Structure
Cytoplasm/Cytosol
Description
Clear, gelatinous fluid that
fills the inside of the cell
Function
Protection and support
EUKARYOTIC ORGANELLES
CYTOPLASM / CYTOSOL
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
http://www.cartoonstock.com/lowres/rjo0
896l.jpg
http://www2.puc.edu/Faculty/Gilbert_Muth/art0063.jpg
EUKARYOTIC ORGANELLES
RIBOSOMES
 Sites of protein synthesis (where the cell produces proteins
according to the directions of DNA)
 Consist of two subunits (small and large) composed of rRNA and
protein
 The individual subunits are synthesized in the nucleolus and then
move through the nuclear pores to the cytoplasm, where they
assemble.
Structure
Ribosomes
Description
Small complex assemblies of
proteins and RNA, often
bound to endoplasmic
reticulum
Function
Sites of protein synthesis
EUKARYOTIC ORGANELLES
RIBOSOMES
http://www.ibri.org/RRs/RR05
1/51cytoskeleton.gif
http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCELL2.ht
ml#Ribosomes
(Both images)
Plant
Animal
Bacteria
EUKARYOTES
•Video: Bioclips
•Click on “Marius Explores The Cell” (10 mins.)
CELL ANALOGIES
FACTORY
CELL ANALOGIES
FACTORY
Cellular Anatomy
Cell Project: Create an analogy of your own!