Download Ecology AS 2.4 Investigate an interrelationship or pattern in an

Ecology
AS 2.4 Investigate an interrelationship or pattern in an ecological
population or community – 3 credits (I)
AS 2.5 Describe concepts and processes relating to ecology – 3
credits (E)
US 6311 Biodiversity – field work – 3 credits (I)
Species definition
A species is a group of organisms that can interbreed and produce
fertile offspring. They share the same gene pool.
A gene pool of a species is the sum total of characteristics that are
found within the species.
Species are made up of individuals that share the same basic
structure, physiology, and behaviour. These are inherited
characteristics that we call adaptations. The life history of a
species also reflects its adaptations (struggle to survive).
Ecological niche
The niche of an organism is it’s role or way of life (job or
profession).
Eg a crab on the seashore is a scavenger.
This is different than its habitat, which is the place where an
organism lives. In human terms it is an organism’s address.
Eg a crab’s habitat is the mid tidal zone on the rocky shore – and
perhaps a certain rock
The habitat should be where the organism has access to
resources, like food, water, space (to live), and members of its own
species (mate).
Adaptations – (behavioural, physiological, structure and life
history) describe what it needs to survive
• Paddle crab on sandy shore (predation) – behaviour hold up
claws to defend, claws structure, paddles to swim, dig
• Barnacle on rocky shore (space) – needs a way of sticking physiological
• Kauri tree in forest (other trees) – behaviour grows tall for light
• Kiwi in bush (predator) – hides in hole - behaviour
• Paramecium in fresh water – contractile vacuole physiological
• Shark in ocean (feeding) – teeth structural
• Neptune necklace (seaweed) – fix itself to rock physiological
• Fantail (eats insect in the air) – structural wings, ability to hover
- behaviour
• Oyster on rock (predation) – structural hard shell. Life history –
produces vast quantities of eggs
• Whelk (carnivorous shellfish) – way to cut into shells structural
Relationship between organisms and their environment
The environment includes all those factors, both living (biotic) and
non living (abiotic), that affect the lives of organisms.
Abiotic Factors
•Light (photo) - duration
•water (hydro) - salinity, speed, humidity
•temperature (thermo)- average, range (eg. rocky shore has
extremes)
•chemical (chemo) - CO2, O2, pH, nutrients
•touch (thigmo) - solid object
•gravity (geo) - orientation in space eg roots go down
•Sound
•Pressure
•Substrate
•Wind
Biotic factors
Interspecific (between two or more species)
•competition for food, water, space, light
•predator / prey
•succession - replacement of one species by another
•plant / animals
Intra specific (within a species)
•competition- for resources, for space, for mates, light, food
•reproduction - pair bond, courtship
•Aggressive - territory, hierarchy
•Cooperation feeding, mating, defence
Populations
A population is a group organisms of the same species that live in
the same habitat.
Measuring Populations
It is difficult to count all the members in a population, so a sample
is taken. The sample should be representative of the population.
To measure the size of a population of mobile organisms, markrecapture is used. Some organisms are captured, labelled (ear
tags, leg bands) and then release them. Later another sample is
taken and population size is calculated from this equation
Size of pop =
Total sample 1 x total in sample 2
___________________________
Number marked recaptured in s2
Some population (rare or shy) sizes are estimated from signs of
their presence (eg footprints, tracks, droppings etc).
Transects
A transect is a line placed across a habitat. The transect is divided
up into intervals and at each interval the population is sampled.
Transects are used where the distribution of the species is affected
by some environmental factor, such as tidal movement. A belt
transect (metres wide) can be used in a forest where organisms
are very large.
Quadrat
A quadrat is a square frame used to isolate an area so the number
of organisms in that area can be counted. The bigger the
organism being counted the bigger the quadrat. Quadrats are
often used along transect lines. If not they should be thrown down
randomly – this can be done by dividing the habitat into a grid and
randomly selecting sample sites.
Community
All plants and animals have two driving forces that make them
what they are (not human). These forces or natures relate to the
drive to survive and the drive to reproduce.
An individual animal does not have to be the best, the fittest, the
strongest or the longest living to make its mark on the world. It
only has to survive to reproductive age and have reproductive
success. An animal or plants genetic makeup means its whole
orientation is to survive and reproduce and this is not selfish – it is
nature.
All biological interactions demonstrate this nature.
Some community patterns
Zonation
Zonation results from the constant change of some environmental
factor across a community.
On the rocky shore the zones are created by the tides. It is the
exposure to air that limits an organism’s distribution.
As the environmental conditions exceed the tolerance limits of a
species, the zone of distribution for a species finishes. Another
species, adapted to the new conditions, forms another zone until it
to can no longer cope with conditions. There is usually an optimum
range where an organism is dominant. In environmental zones
where the organism is under stress other species better suited will
out compete them. Competition between species where they meet
means zone are usually quite distinct eg tubeworms or oysters on
the rocky shore. On the rocky shore it is the sessile organisms
that dominate.
Zone distributions are often portrayed on kite diagrams. These are
obtained by taking quadrat samples along a transect line across a
community.
Succession
Succession is the change is species composition in an area over
time. During succession, one species starts to grow and modifies
the environment so another organism can grow in its place. This
cycle continues until a climax community is established. Primary
succession differs from secondary succession in that it occurs in
an area that has had no previous vegetation (e.g. a larva flow like
Rangitoto Island) where as secondary succession takes place in
an area that has a soil layer but has been cleared for some
reasons (e.g. by fire)
Ecology
Energy Flow
Food chains show the flow of energy through an ecosystem. For
example on the rocky shore algae that settles on rocks is scrapped
off by snails which in turn are eaten by oyster borers which are
eaten by birds
Algae
> topshell > oyster borer
> sea bird
Producer – primary consumer – secondary consumer
3rd trophic level
1st trophic level - 2nd trophic level In reality feeding relationships are more complicated. A food web
shows all the feeding relationships in an ecosystem. Energy can
only go in one direction and it is passed from one trophic level to
the next.
Biodiversity
The biodiversity of an ecosystem comprises the sum total of
different types of species found within. The variety of life in all its
forms, including ecosystem diversity, species diversity and genetic
diversity, and their relative abundance in particular habitats.
SWOT (strengths, weaknesses, opportunities, threats) analysis of
biodiversity in NZ.
S (of increased )
• Greater tourism
• Healthier ecosystems – more complex food chains
• More stable to change (storms, pollution)
• Less extinction
W (of decreased biodiversity)
• More vulnerable to change
• More extinctions
• Unhealthy
O (of increased biodiversity)
• more habitats and niches
• greater use by humans (manuka experiment)
T (to biodiversity)
• pests (introduced species like possums, stoats, rabbits)
• people overfishing or overfarming or making money at the
expense of future planning.