Organisms and Environment

What its all about!

Terms

• Habitat

The place in which an organism lives

Terms

• Environment– All factors in the

surroundings that affect an organisms chances of survival and reproduction

Terms

• NicheAn organisms

way of life or role in the community

Terms

• Adaptation– Inherited

characteristics that increase the chance of survival and reproduction

The Environment

• Biotic– Other organisms

• Food• Predators• Parasites• competitors

The Environment

• Abiotic– Physical influences

• Temperature

• Light intensity

• pH

• Water supply

• Wind factors

• Salinity

• Humidity

• Minerals

Temperature• Affects activity of enzymes

– Homeothermic animals maintain body temperature

– Cold temperatures affect life styles– Adaptations

• Dormancy• Hibernation and aestivation• Diapause• Migration

Light

• For Photosynthesis (plants)– Causes competition

• Source of information (animals)

• Indicates photoperiod

• Indicates low relative humidity

Mineral ions

• Low concentrations– Resource for plants

• High concentrations– Influence water concentrations

• Key role in distribution of animals and plants

Salinity

• Marine organisms need constant salt concentration

• Fresh water organisms must remove excess water due to low salt

Oxygen

• Terrestrial organisms above ground - not a limiting factor

• Marine and freshwater organisms - little oxygen present

• Aerobic = oxygen present

• Anaerobic = oxygen absent

pH

• Between 3 and 9

• High pH inhibits metabolism

• Affects solubility of certain ions

Relative Humidity

• Low humidity causes desiccation

• Three factors– Lower relative humidity means more rapid

evaporation– Outer body layer (exoskeleton, hair) – Surface area to volume ratio

Water Flow

• Delivers oxygen

• Washes organisms away

Range of Tolerance

• Range of physical conditions in which an organism can survive

• Physiological tolerance– Organisms tolerance in lab.

• Ecological tolerance– Tolerance of biotic and abiotic factors

Intensity of Condition

Perf

orm

ance

of

Sp

ecie

s

Growth

Reproduction

Survival

Biotic Environment

• Competition

• Exploitation

• Predation

• Parasitism

• Commensalism

• Allelopathy

Competition

• When demand exceeds supply

• Density dependant– Decreases reproductive rate– Reduces population numbers

Intraspecific Relationships

• Within species• For

– Food– Mates– Breeding territories– Space– Light– Minerals

Competition for Mates

• By males– Fighting– Display

• Strong selective pressure for competitive ability– Sexual dimorphism

Competition for Territory

• Territory occupied and defended– C.f. home range - area from which animal

does not stray but is not defended

• May be:– Defended all year (NZ Robin)– Site to build nest (Pukeko)– For mating (gannet)

Avoiding Competition

• By dispersal– Passive (fungi & plants) - high mortality

rate

• Different stages of the life cycle occupy different niches

Interspecific Relationships

• Competition between species– Exploitation– Predation– Parasitism– Mutualism– Commensalism– Antibiosis

Competitive Exclusion Principle• Gauses Principle

• Two species cannot share the same niche indefinitely in the same habitat

• Niche - sum total of an organisms requirements

• Habitat - where an organisms lives

Niches

• Fundamental niche– Range of conditions in which an organism

can survive under protected conditions

• Realised niche– Conditions required in the wild– Usually a narrower range

Exploitaiton

• One species benefits at the expense of another– Predation - one organism kills another– Grazing - one organism kills part of another– Parasitism - one organism feeds off

another (the host)

Predation

• Short term– Influence each others population numbers

• Long term– Influence evolution because under

selective pressure

Parasitism

• Depends on host for food

• Host not killed

• Ectoparasites live outside host

• Endoparasites live inside host

• Parasitoids - one insect feeds off another

Mutualism

• Partnership with another species

• Both benefit– Lichens - fungus and alga – Root nodules– Micorrhiza– Gut mutualists

Commensalism

• One organism benefits, the other is not affected

Allelopathy or Antibiosis

• One organism produces a chemical that inhibits the growth of potential competitors

Summary of Interspecific Relationships

Species A Species B

Competition - -

Exploitation + -

Mutualism + +

Commensalism + 0

Antibiosis + -

Explaining Niche

• Where it lives

• What it eats

• How it responds to stress

• What limits its population growth

Pikau (Golden sand Sedge)

Harakeke (flax)

Kiwi

Tui

Weta

Adaptations

• Structural (morphological)– Body shape, colour, apendages

• Behavioural – Nocturnal, diurnal, spitting, hiding, stinging

• Physiological (metabolism)– Tolerate high temperature, salinity

• Life history– Reproductive strategies

Kauri Snail

Kaki (Black Stilt)

Bat

Hector’s Dolphin

Shrubby Tororaro