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Figure 50.13 Zonation in the marine environment
Life on Earth - Timescale
3.4 BYA - heterotrophs
2.7-2.2 BYA O2 begins to
Accumulate
2.2 BYA first Eukaryotes
700 MYA sharp increase in
Atmospheric O2. Reached
modern levels in Cambrian
570-510 MYA
450 MYA life on oceans
surface and on to land
Life on Earth
•  Living things cause change
•  Living things respond to change
•  Living things change their environments
•  Living and non-living components of our Earth
interact
•  Processes like global warming/climate change
follow large-scale patterns, but it is the composition
of life on earth that can affect those patterns
•  Ecological systems exist in balance - that balance
can be disturbed, and its evolution from there can be
difficult to predict.
Life - as we know it
•  Organized internal structure - share a similar chemical
composition
–  Composed of a common organization of atoms, molecules, cells... with
emergent properties.
•
•
•
•
DNA/RNA
Respond to stimuli, coordinated growth and development
Capture and transform energy from their environment
Maintain internal conditions separate from external
–  Composed of cells
•  Arise through reproduction
•  Can adapt through mutations and adaptations
•  Effect change on their environment
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Organic compounds
Photosynthesis/Respiration
Photosynthesis:
•  Plants use carbon
dioxide and produce
starch and oxygen
Respiration
•  Animals use starch/
sugar and oxygen, and
produce carbon
dioxide
H2O + CO2 = Starch/sugar + O2
Starch/sugar + O2 = H2O + CO2 2-7
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Photosynthesis
•  The synthesis of organic compounds (sugars) from simple
inorganic compounds (CO2 and H2O) in the presence of
chlorophyll using light energy from the sun.
–  General Formula for PS
–  The Organs of Photosynthesis - Leaves and
Chloroplasts –  Chloroplast Structure and Photosynthesis
6CO2 + 6H2O +
•  The Light Dependent Reactions
•  The Light Independent Reactions (Dark Reactions)
•  Coupling the Light and Dark Reactions = C6H12O6 + 6O2
–  Photosynthetic Pigments and the Electromagnetic
Energy Spectrum
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photosynthesis/Respiration
Photosynthesis:
•  Plants use carbon
dioxide and produce
starch and oxygen
H2O + CO2 + SUN = Starch/sugar + O2
Energy pyramid
Figure 2.15
Respiration
•  Animals use starch/
sugar and oxygen, and
produce carbon
dioxide
Starch/sugar + O2 + ATP
= H2O + CO2 6CO2 + 12H2O + sunlight ---> 6O 2 + C6 H12O 6 + 6H2O
2-13
Source: Data from Howard T. Odum, “Trophic Structure and Productivity of Silver Springs, Florida” in Ecological Monographs,
27:55-112, 1957, Ecological Society of America.
Biomagnification
Energetics predicts few top predators.
Not enough energy at top trophic levels
Top predators are also often K-selected
(low reproductive rates/output.)
Biomagnification is process that
concentrated toxins at high trophic levels
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Two Main Classes of Cells
Eukaryotic Cell (animal) Prokaryotic Cell (bacteria)
•  Prokaryotic (Bacteria and Archaea)
–  Pro = “Before”; Karyon = “Kernel”
–  No nucleus, DNA coiled up inside cell
•  Eukaryotic (Everything else)
–  Eu = “True”
–  DNA inside membrane bound organelle inside
cell, the nucleus
Basic Properties of Molecules in
Motion
Osmosis- passive transport of
water across a membrane
•  Diffusion: the random movement of molecules
from a region of high concentration to a region of
low concentration. –  Concentration gradients
•  Osmosis: the diffusion of water…
–  Osmotic pressure
–  Isotonic, hypotonic and hypertonic
environments for plant and animal cells
Osmosis: problems with salt
Isosmotic
•  Osmoconformers - change with outside
salinity
•  Osmoregulators - regulate internal saltiness
separate from the outside
•  Isosmotic: same inside and outside
•  Hyperosmotic: saltier inside
•  Hypoosmotic: saltier outside
Sea Cucumber
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Hyperosmotic: fresh water fish
Endothermy in fish!
?
Hypoosmotic: Marine Fish
Reproductive strategies
SEX (meiosis):
NO SEX (asexual)
•  Internal fertilization
•  Fission - parent splits
(few or many)
•  Budding - parent
•  Nest laying (brooding)
develops small growth
•  Broadcast spawning
(mass release)
This is mixing genes!
This is cloning!
Sex?
Sexual reproduction
•  Introduce new genes
•  Diversity in phenotype
and genotype
•  Resistance to disease
•  Resistance to
environmental change:
Adaptation
•
•
•
•
•
Hard to find a mate
Picking the right one
Mutations/problems
Parental investment?
Don’t know exactly
what you get
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Sex?
Some can do both!
Asexual reproduction
•  Fast
•  No diversity (easily
wiped out)
•  Know exactly what
you get
•  Problem (if one exists) is
reproduced
•  Can spread your exact
•  Need a self recognition
genes
mechanism
•  Cover an area quickly
•  No need to find a mate
•  Combination of sexual and asexual
reproduction can bring the best of both
worlds
•  Hermaphrodites: no need to find the right
sex! These are organisms that are both
sexes at once, or can change from male to
female or female to male.
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Reproductive strategies
Populations: what affects their size
and growth?
•
•
•
•
•
•
•
•
3-10
Density (#/area) - carrying capacity (K)
Natality - birth rate
Mortality - death rate
Age distribution/sex ratio
Spatial distribution
Resource availability
Species interactions
Migration/emmigration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Population oscillations
Predator-prey oscillations
Figure 3.18
Figure 3.19
3-7
3-8
Source: Data from D. A. MacLulich, Fluctuations in the Numbers of the Varying Hare (Lepus americus), Toronto: University of
Toronto Press, 1937, reprinted 1974.
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
J and S population curves
Competitive exclusion
Figure 3.20
3-9
Major Components of the
Environment
•  Abiotic components, which consist of
nonliving chemical and physical factors,
such as temperature, light, water, minerals,
and air
•  Biotic components, which include the living
factors—all the other organisms that are
part of an individual’s environment.
Species Interactions (Biotic):
Interspecific and Intraspecific
•  Competition
–  Competitive exclusion
–  Resource partitioning
•  Predation
•  Symbiosis
–  Mutualism
–  Parasitism
–  Commensalism
Zooxanthellae: the key to coral reef productivity
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Speciation, adaptation, and competition
What about analogous
structures?
•  Co-evolution
•  Convergent evolution
What is a niche?
Competition for resources leads to:
• Competitive exclusion (one ‘wins’) or
• Resource partitioning: the resource is ‘shared’
Adaptation by the process
of Natural Selection
• Survival and differential reproductive
success over a period of time
• Traits that increase ‘fitness’ are ‘selected
for’, and are passed on through generations
Ecosystem structure
Predators: Sea Otters
•  Keystone species - is there such a thing? –  A species whose ‘role’ or niche has a major
impact on the structure of an ecosystem
–  Some case studies?
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Sea Otters and Sea Urchins:
a kelp forest paradigm
Ecosystem change: an example
Sea Urchins eat kelp, especially new recruits
If kept in check, they eat drift kelp
If populations expand, they will eat established kelp
Sea Otters eat urchins, especially exposed ones
They will keep sea urchin populations in check
The Aleutian Island studies
Sea Otters as a keystone predator
Reduction of coral = increase in
Algae. This shifts functional Groups of species, and affects
Primary productivity
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