Chapter 4
Do Now

 Name one difference between a plant cell and an
animal cell
 What is the purpose of a cell membrane?
 What type of cells do we have? A) Prokaryotic B)
Eukaryotic
Objective

 SWBAT: Identify levels of organization from cell to
ecosystem
 Describe the challenges that marine organisms face
living in the sea
 Describe the process of osmosis and determine what
makes active transport different from passive
transport.
Types of Organisms


All living organisms can be divided into two basic
groups based on cellular composition:
1. Prokaryotic
2. Eukaryotic
Types of Organisms

 Prokaryotic Organisms:







Lack a nucleus
Posses ribosomes
Contain a circular ring of DNA
Some may also have plasmids, extra pieces of DNA
Cell wall is normally present
May have a flagellum
Unicellular


Types of Organisms

 Eukaryotic Organisms
 Possess DNA enclosed inside a nucleus
 Posses many specialized organelles (look at organelles
in Fig. 4.8)
 Eukaryotic organisms can be unicellular or multicellular
Levels of Organization in Living
Organisms

 Atom – fundamental unit of all matter
 Molecule – two or more atoms chemically joined
together
Levels of Organization in Living
Organisms

 Organelle – specialized features of cells
 Cell – basic unit of life
Levels of Organization in Living
Organisms

 Tissue – group of cells functioning as a unit
 Organ – many tissues arranged into a structure with
a specific purpose in an organism
Levels of Organization in Living
Organisms

 Organ system – group of organs that work together
 Whole organism (individual)
Interactions among
individuals

 Population- A group of
organisms of the same
species that occur
together
 Example
Interactions among
individuals

 Community- all the
populations in a
particular habitat
 Example
Interactions among
individuals

 Ecosystem- A
community of
communities in a large
area, together with
their physical
environment
 Ecosystem
Challenges of life in the sea

 Planktonic organisms (drifters)
 Benthic organisms (bottom dwellers)
 Nekton (strong swimmers)
 Many adaptations are made to maintain internal
body conditions
 Homeostasis
Salinity

 Enzymes and organic molecules are sensitive to ion
concentration
 Diffusion and Osmosis
Diffusion

 In solution- ions & molecules move around like
water molecules
 Random movement spreads them out until they are
evenly distributed.
 Result: molecules move from areas of high
concentration to low concentration

Diffusion and cells

 Internal composition differs from external in the cellsubstances will move into or out of the cell by
diffusion
 If more sodium in outside the cell – sodium will
diffuse into the cell
 Problem if organism is sensitive to sodium
Diffusion and Osmosis

 Since marine organisms live in a very solute-rich
environment, they have a tendency to gain solutes
and lose water
 This can result in the death of cells if the water
loss/solute gain is significant
 These organisms must find ways to deal with this
diffusion and osmosis
Membrane barrier

 Membrane blocks the passage of the common ions in
seawater and many organic molecules.
 Membrane allows exchange with many molecules
such as O2 and CO2
 Selectively permeable – only some substances enter
and leave
Osmosis

 If the solutes are higher outside of the cell than
inside of the cell, water will rush out of the cell.
 Cell will shrink
 http://www.youtube.com/watch?v=sdiJtDRJQEc
 Discovery Ed simulation
Osmosis

 The movement of water across a selectively
permeable membrane
 If the total concentration of solutes inside a cell is
higher than the outside the cell, water will rush into
the cell.
 Cell will swell
Active Transport

 Proteins in the cell membrane pump materials in the
opposite direction to which they would move by
diffusion.
 Requires energy
 What form is that energy in?
 How often do we use active transport?
 Over 1/3 of a cells total energy expenditure
Active Transport

 What is needed to move molecules into or out of a cell against the
gradient?
 What are cell membranes made of?
 What is imbedded in the cell membrane?
 ATP has “trapped” energy from what process?
 Active transport brings in materials to the cell and what else does it do?
 Discovery ed Simply Science: Matter and Energy on the move active
transport
Regulation of Salt and
Water Balance

 Some marine organisms do not actively maintain salt
and water balance
 Salinity changes with salinity of water –
Osmoconformers
Osmoconformers

 If an osmoconformer were placed in a freshwater
environment, the would swell and burst.
 Water would rush into the cell because water would
move into the cell (low concentration)
 Open ocean is where you find osmoconformers
Ways to adapt

 Adjust solutes in your body to match solutes of
water outside the body.
 Total amount of dissolved material needs to be the
same
 Change the amount of one particular chemical to
match changes in salinity outside
 Sharks- increase/decrease urea in their blood
 Danasliella-single celled marine alga – changes
glycerol
Osmoregulation fresh vs
marine

Osmoregulation

 Marine birds, reptiles and plants have special cells or
glands to get rid of extra salts.
 Marine plants have cell wall to help regulate
swelling caused by osmotic water gain
Vocab

Exit Ticket

 What is the difference between osmosis and
diffusion
 How do marine fishes deal with the the water they
constantly loose to the salty environment they live
in?
 What is a population?
 What is a community?