BIOL1131 Lecture Notes - Lecture 3: Vertebral Column, Necturus, Myelin
7 Jun 2018
School
Course
Professor
Resources, phenology and climate change
• What is a resource?
o Something that can be reduced by the activities of an organism –
something in short supply
o Two types of resources:
▪ Biotic (organic) – derived from other forms of life
▪ Abiotic (inorganic) – derived from ecosystem and
biosphere processes
o Resources fluctuate in space and time on all scales
o Resources can vary predictably over time or unsystematically (e.g.
after natural disasters)
▪ Systematic, predictable variation – fixed pattern of
response
▪ Unsystematic, unpredictable variation – plastic responses;
organisms can alter their growth rates, reproductive phases
and behaviour
• Resource pulses
o A brief, infrequent even of high resource availability
• Principle of resource allocation
o Organisms use energy to acquire resources (e.g. when foraging) –
resources are allocated among competing life functions
o Resources are split between:
▪ Reproduction
▪ Growth
▪ Defense
▪ Homeostasis (maintenance)
o The allocation of these resources depends on the amount of
resources available
• The competitive exclusion principle
o Both species do well when grown separately
o When the species are grown together, one is excluded from the
culture
o Two species with the same limiting resource cannot coexist
• How do very similar species coexist in nature?
o They have different ecological niches
o Fundamental niche – defined by all the biotic and abiotic factors
that affect survival of a species
o Realised niche – a part of the bigger fundamental niche
▪ Vertical stratification of each species is a result of
environmental tolerances and interactions among species
o Niche breadth – is the range of a resource that a species uses
o Competition occurs when niches overlap
▪ Resource partitioning is a mechanism that minimizes niche
sharing, e.g. forest birds feeding at different heights above
ground
▪ Morphological changes that assists resource partitioning
are promoted by natural selection
• Seasonality
find more resources at oneclass.com
find more resources at oneclass.com
o Strong contrasts in the weather regarding the seasons
▪ The higher latitude, the higher seasonality
o Responses to weather are short-term, whilst responses to climate
usually involve adaptations
• Australian Conditions
o Two-thirds of Australia is desert
o Rainfall is highly variable
▪ Desert ecosystems are productive in pulses after rain
▪ Consumers must
▪ Adopt a pulse and reserve pattern
▪ Eat reserves of other organisms
▪ Adopt opportunistic feeding habits
• Hopkins Law of Phenology
o Phenology differs by four days for every degree of latitude, every 5
degrees of longitude and every 30m of altitude
• Why is reproductive often seasonal?
o Energy demands and availability vary annually
o Reproduction is energetically costly – in seasonal environments
offspring production is timed to coincide with peak energy
availability
• Trophic mismatch
o Timing of resource demand does not overlap with the peak of
resource availability
o Can occur when the consumer and producer are responding to
different environmental cues, or if species respond differently to
similar changes in climate
• Timing of events: plants
o Daily cycles of light and dark provide a constant stimulus that
regulates the growth and development of many species
o Response to the length of light and dark period, photoperiodism,
allows plants to reproduce synchronously in the appropriate
season
• Timing of events: insects
o Photoperiod – especially for hormones important to pupation or
diapause (dormancy)
• Timing of events: vertebrates
o Reproduction typically triggered by changing daylength
o Pineal gland – photosensory cells in fish, amphibians and some
reptiles
o Secretory pinealocytes in birds, mammals and snakes produce
melatonin derived from serotonin
• Global warming: predicted loss of biodiversity
o Extinction risk of 20-30% of plants and animals
o Expected shift in species distributions – change of ˚C of 50km in
latitude of 500m in altitude
• EXAM QUESTIONS ON THESE
o Post E & Forchhammer MC 2008. Climate change reduces
reproductive success of an Arctic herbivore through trophic
mismatch. Proc Roy Society Series B 263: 2367-2373
find more resources at oneclass.com
find more resources at oneclass.com
