Transcript Biodiversity

Based on the interrelationships among organisms, what makes some
organisms more successful than others at surviving?
What is a Shoal?
 Large numbers of fish of the SAME species and approximately the SAME
size.
 Referred to as a ‘school’ when the group of fish is swimming together in a
coordinated way.
Benefits of Shoaling
1. Hydrodynamic efficiency


Groups of fish save energy when swimming together
Individuals obtain reduction in drag by following in “slip-stream” of
neighbors
Benefits of Shoaling
2. Predator avoidance:
a) Confusion effect: It is difficult for predators to pick out individual prey
from groups
b) Many eyes effect as size of group increases, the task of scanning for
predators can be spread out
Benefits of Shoaling
3. Foraging Advantages : Time taken to find food is decreased
4. Reproductive Advantages: Provides increased access to potential
mates
Examples of shoalers
 Skipjack tuna and sardines
 When threatened, sardines form massive “bait balls” of hundreds or
thousands!
 Skipjack tuna forms shoals of up to 50,000!
Types of shoalers
 Fish can be obligate or facultative shoalers:
 Obligate – spends all their time shoaling or schooling and may become
agitated when separated from the group (examples: tuna, herring, anchovy)
 Facultative – shoal only some of the time, perhaps only for reproductive
purposes
(examples: Atlantic cod)
What is Succession?
 The gradual process of change that occurs in community structure over a
period of time
 Example
Succession
 As plant communities
change the animal
communities change.
Succession at Hydrothermal Vents
 One of the first animal species to inhabit the area
around a hydrothermal vent is the tube worm Tevnia.
 Tevnia is replaced by the larger and faster growing tube
worm Riftia.
Riftia tubeworms can
grow up to two meters
long. This adult
tubeworm that has been
removed from its white
tube.
Riftia
Tevnia
 Tevnia are usually white,
but this clump of worms is
stained brown from iron in
the vent fluids. The largest
worm in this clump (with
more white color) is a
different species - a Riftia
tubeworm.
Biodiversity
 Takes into account:
 # of different species present
 Range of habitats and ecosystems
 Examples:
CORAL REEFS
High biodiversity w/
many species present
SANDY SHORE
Low biodiversity w/ few
species present
Quadrat
 A square used in ecology and geography to isolate a sample, usually about
1m2 or 0.25m2
 Used to investigate the diversity of organisms in a suitable habitat
(example: rocky shore or sandy shore)
Extreme & Unstable Environments
Tend to have LOW biodiversity!

Example 1: Sand on a reef slope (unstable)
 Easily dries out
 Easily eroded by wind and water currents
 Animals here have to living in sediments in order to survive (Infauna)
 Worms, clams, sand fleas, crabs, etc.

Example 2: Hydrothermal vents (extreme)
 Extremely high pressure
 High temperature
 Few organisms adapted to these conditions
 Lack of sunlight
 Bacteria, tube worms, crabs, fish, mussels, clams
Stable & Favorable Environments
Tend to have HIGH biodiversity!

Example: Coral Reefs
 Balance between predators and prey (sharks feed on sick & dying; keeps a
strong healthy population of small reef fishes)
 Algae = primary producers (zooanthellae inside coral polyps & algae
growing on the reef)
Organisms found here:
Sharks, groupers, snappers,
worms, butterfly fish, urchins,
sea stars, algae, corals, anemones,
turtles, sponges, etc.
Specialized Niche
 Narrow range of food
Generalized Niche
 Exploit a wider range of food
requirements
 Live in specific habitat
sources
 Live in wider range of habitats
Example: Butterfly fish
 Territorial
 Live closely w/corals and
anenomes
Ex: Tuna
 Migratory
 Feed on many different species
of fish
Why do habitats with high
biodiversity tend to contain
narrow ecological niches?
 Each species has its OWN niche within the ecosystem
 High biodiversity means that many different
species live within one ecosystem.
 What would happen if the niches overlapped?


INTERSPECIFIC COMPETITION and one species will die out!
Narrow niches reduce overlap and therefore reduce
competition