Transcript Habitat

Habitat
Chapter 9 p268
Geographic Distribution
• Geographic distribution: the places where a
particular species can be found.
• Geographic distribution of a species changes
over time due to:
– Macro climate change
– Catastrophic events
– Human intervention
• Weeds/feral animals/pests
• Land clearing for urbanisation, farming and forestry
EXAMPLES OF DISTRIBUTIONS
The kultarr (Antechinomys
laniger)
The Numbat
(Myrmecobius fasciatus)
The cane toad (Bufo marinus)
The habitat of the tamar wallaby
Habitat
• Habitat: The type of place an organism lives.
– The ‘address of an organism’
– Generally classed as either terrestrial (land) or aquatic
(fresh, salt-water or estuarine (mouth of rivers)
• Patterns of migration can affect habitat.
• Microhabitat:
– A habitat within a habitat.
– Within a habitat there will be slightly different
localised environmental conditions.
Microhabitat examples
• Pockets of moisture or humidity. The trunk of
the Dicksonia Antarctica (tree fern) is a
microhabitat for fungi, ferns, moss, liverworts,
spiders and insect.
• The muddy floor of a lake.
Habitats are not uniform
• An organisms’ habitat is not the same
throughout. Some areas may provides food
resources, others shelter and protection and
others places to reproduce and bring up
young.
Range
• Range: The geographic extent or area that a
species inhabits.
• It encloses all of the habitats where a
particular species lives.
• A large range does not mean there are many
animals and a small range does not mean
there are few.
Migration: Moving between habitats
• Many species move (migrate) between
habitats in order to secure food, breeding sites
or to avoid unfavourable climatic conditions.
• Migration can be seasonal (annual) or once in
a lifetime.
Migration of the humpback whale
The Bogong Moth
(Agrotis infusa)
The bogong moth migrate to
mountain crevices at altitudes
over 1500m during the winter.
They undergo diapause – a
state of inactivity
characterised by low
metabolism.
Niche
• Niche: The limits, for all important environmental
features within which individuals of a species can
survive, reproduce and may persist indefinitely.
or
• The role of a species within a community.
• ‘Where various species differ in their use of food
and space resources available in a habitat they
are said to occupy different niches’
(See Black Swan and Chestnut teal duck example
p280)
Niche
• The structural features of an organism (e.g.
Having a long or short beak) will relate to how
it can exploit its habitat and therefore its
niche.
Describing Niches
• There are different ways
to describe a niche. E.g
Feeding niches
Niche overlap
• Niche overlap between different species does
not generally occur for extended periods of
time.
• This is because niche overlap would create
intensive competition and one species would
eventually outcompete the other.
Environmental Factors
• Abiotic environment: the physical
surroundings such as soil, rainfall,
temperature, salinity and nest sites.
• Biotic environment: other organisms with
which an organism interacts. It could include:
availability of mates, predators, parasites and
food supply.
Commonly measured environmental
factors
Air
Water
Soil
Temperature
Dissolved oxygen
pH
Humidity
Dissolved nutrients
Salinity
Rainfall
Salinity
Dissolved oxygen
Wind speed
Tidal movements
Dissolved nutrients
Light intensity
Turbidity/Clarity
Organic content
Concentration of carbon
dioxide
Temperature
Texture (clay, loam, sandy
etc)
Micro-environments
• Environmental conditions can vary within a
localised area and these areas are called
micro-environments.
• For e.g. In hot, dry conditions, the underside
of a leaf is exposed to differences conditions
compared with the upper side.
Tolerance Range
• Tolerance range: the range of conditions
(nutrient levels, water, oxygen, carbon dioxide,
light and temperature) in which an organism
can survive and effectively function.
– The tolerance range of a species directly
determines the distribution of that species.
•Beyond the tolerance range for temperature, these fish cannot survive.
Environmental factors limit species
distribution
• Limiting factor: An environmental factor
which is an essential requirement for an
organism and which is in limited supply is
called a limiting factor.
Examples of limiting factors
Case Study: Distribution of marine life
on rocky shores
• Rocky shores are subject to specific
environmental factors which limit the
distribution of species by creating habitat
boundaries.
• Rocky shores are zoned according to the
influence of the tide.
• The effects of wind, sunlight and
temperature also influence marine life in
each zone.
Algae of the subtidal zone
• Brown kelp attached to rocks – have long
photosynthetic fronds which are buoyant
(float).
Organisms of the intertidal zone
• Sea grapes or Neptune’s necklace – are
protected from dry conditions at low tide by
sticky mucus covering and water filled
bladders. Abundant on the southern coast
of Australia.
• Herbivorous and carnivorous molluscs
• Barnacles
• Rock pools provide protection for sea stars
and crustaceans.
Life in the spray zone
• Splash from sea spray and extreme high tides
evaporates during the heat of the day
concentrating salt on the rock. Combined
with low temperatures at night few species
can tolerate these conditions.
• E.g. Cyanobacteria (blue-green algae),
crustose, grey, orange and yellow lichen and
snails can survive here.
Adaptations
• An adaptation is a feature of an organism that helps
it survive in its particular environment – that is, live
long enough to produce viable offspring.
• Adaptations may be behavioural, structural or
physiological.
Behavioural adaptations
• Are observable activities/responses
Examples:
• Moving out of the sun into the shade
• Migrating to avoid a cold winter
• Huddling together for warmth
Structural Adaptations
• Are anatomical features
Examples:
• Insulating layers of fur or fat
• Presence of sweat glands in skin
• Body shapes with differing SA:V ratios
Physiological Adaptations
• Are those that relate to the way in which a
living organism or body part functions
Examples:
• Increasing/decreasing metabolic rate
• Dilation/constriction of arteries
• Producing more red blood cells at altitude
where O2 pressure is lower
Australian Environments
• Terrestrial (land) and aquatic (fresh and
saltwater) environments. Australian
terrestrial environments vary due to climate
and latitude:
• Northern latitudes are tropical
– high summer and year-round rainfall, high
humidity
– tropical rainforests along coasts
• Inland are semi-arid to desert:
– low rainfall, extreme high and low temperatures,
low humidity
– semi-arid  desert
– sparse vegetation
• Southern latitudes are temperate
– moderate rainfall and humidity, average
temperatures with some extremes
– snowfall in areas high above sea level and parts
of Tasmania
– four season climatic pattern
Australian Environments (cont..)
• Australian soils are nutrient deficient because
they are old and weathered.
• Marine environments are ecologically diverse.
• Some freshwater sources may dry up in
summer or in drought.
Vegetation Types
Australian vegetation can be classified according
to:
1. The type of plant that forms the dominant
layer.
2. Density or canopy cover – Estimated based on
the amount of sunlight blocked out.
•
Open forests – less than 30%
•
Closed forests – more than 70%
• Distribution of Australian vegetation types
Surviving in the Australian
Environment
• Deserts are distinguished by very low rainfall
compared with high water loss through evaporation.
• They can be hot or cold deserts.
• Australia has the greatest percentage area of desert
of any continent.
• Australian deserts generally have high temperatures
and sunlight and low rainfall.
Plants in arid environments
Adaptations for reducing water loss
• Xerophytes (‘lovers of dryness’)
– are adapted to living in dry conditions
– leaves avoid water loss and increase in internal heat
• Include succulents and sclerophylls (hard leaved) plants
• Sclerophylls leaves:
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thick waxy coating
hairs covering stomata
reduced leaf surface area to volume ratio
orientation of leaves away from suns rays
Leaf cuticles and hairs
• A thick cuticle (waxy outer layer) reduces
water loss by reducing diffusion through the
epidermis.
• Leaf hairs reduce water loss and surface
temperature by creating a still layer of air
along the leaf surface decreasing the water
concentration gradient between the air and
the leaf.
Distribution of stomata
• Fewer stomata which are often in sunken in
grooves or pits close during the hottest part of the
day to reduce water loss.
Reduced surface area and leaf orientation
• Thin to needle-like leaves (e.g. Hakea).
• Eucalypt leaves hang vertically downwards and are
orientated so that the edge of the leaf faces the
midday sun. They are isobilateral because they
have stomata and photosynthetic cells on both
sides of the leaf.
Halophyte adaptations
• Halophytes (‘lovers of salt’)
– Tolerant of high salt levels
– Usually succulents
– Coastal ecologies
• Water loss through transpiration causes salt
to transported from the roots to the leaf.
Excess salt causes loss of turgor, stomatal
closure and reduction in transpiration and
CO2 uptake.
Physiological adaptations and surviving salinity
• Salt tolerant plants regulate salt levels by
controlling salt absorption and isolating salt within
the shoot.
• Physiological adaptations:
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Higher osmotic pressure in cytoplasm
Exclusion of salt from leaves
Return of salt to roots
Dilution of salt by increased shoot growth
Shedding salt-laden leaves
Excretion of salt from salt glands
Australian fauna: Survival in the desert
• The three main challenges for Australian desert animals are
body temperature, water and salt balance.
• Temperature regulation in desert animals can be assisted by:
– Behaviour which increases or decreases heat exchange with the
environment
– Changes in circulation of blood in the skin effecting the rate of heat
exchange
– Increased or decreased production of metabolic heat
– Evaporative cooling through panting or sweating (can also be a
problem)
Reptiles – winners in the desert
• Reptiles need to gain all their heat from the
environment.
• They have strong behavioural adaptations for
thermoregulation such as those shown
below with the example of the Australian
agamid lizard:
(See chapter 10)
• The thermoregulatory behaviours this lizard will
show are:
– To raise body temperature it lies on a rock in full sun at
right angles to the sun’s rays.
– To lower body temperature its lies parallel to the sun’s
rays minimising exposed surface area. It also retreats
beneath a rock or burrow.
Sleeping through bad times
• Torpor - is when animals (fishes, frogs,
lizards, birds, bats and mice) lower the body
temperature and become inactive or
dormant for a period of time.
• Frogs in the semi-arid zone burrow beneath
ground and remain dormant in periods of
drought. The water holding frog cocoons
itself in its own skin filled with water.
Escaping the cold- hibernation
• Hibernation – extended torpor usually to escape
cold.
• Hibernation is triggered by:
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scarcity of food
decrease in temperature
hormonal responses to decrease in light
occurs during sleep
• Hibernation is characterised by:
– decrease in body temperature (always above freezing)
– decrease in heart rate (3-10bpm)
– respiration rate reduced and periods of no breathing
• During hibernation:
– an animal is sensitive to changes in
environmental conditions:
– e.g a lowering in external temperature 
increase in circulation  increase in respiration
 increase in metabolic activity
• Waking from hibernation:
– increased circulation to some organs
– increase metabolism and heat production
– increase body temperature (sometimes rapid)