INTRODUCTION

1. Rationale and approach

The body of ecological literature has escalated over the last 100+ years. Initially it was–

  • descriptive ecology followed quickly by basic quantitative methodologies, and then vegetation mapping that started the revolution
  • then population and community approaches with specialisations in wildlife management and environmental economics became fashionable
  • followed by ecosystem studies and biogeochemical recycling/productivity - withprogrammes on co-evolution and convergence between climatically similar continental systems, and behaviour and capture/relocationstudies of vertebrates
  • then ecophysiology, followed by molecular and mathematical specialisations becamemore fashionable as the technological revolution enabled ecologists to ask and answer many different and extremely complex questions.

At about this time fieldwork became “a luxury rather than a necessity” and many ecological studies became laboratory and/or computer-based. Today ecology encompasses a whole rangeof disciplines, and is multi-, inter- and trans-disciplinary, with a focus on–

  • Common Property resource management and Intellectual Property rights (a socio-political dimension, e.g. PLAAS)
  • Biodiversity Conservation and Global Climate Change (a conservation and biosphere dimension, e.g. SANBI)
  • sophisticated GIS, and data collection and retrieval systems aimed at the monitoring

and evaluation of impacts locally, regionally an globally (where policy issues and legislation are key drivers, e.g. Richard Knight’s group here at UWC)

  • and there are other specialisations… (e.g. such as the BotSoc, Wildlife Management Association, IUCN, Agriculture and Forestry, DWAF and WfW, DEAT, CapeNatureand SANParks, etc.)

Despite all this we have yet to master adequate monitoring and implementation(despite the huge knowledge base), at not only local but at global levels. We as Homo sapienshave still to deal with the NUMBER ONE issue which is over population and over consumption by our own species (currently at about 40% of total global net productivity – which is in the region of 60% terrestrial productivity).

Through time, and especially over the last few hundreds years, we have created a bewildering variety of ecological issues/crises with unforeseen downstream environmental impacts. As our theoretical ecological knowledge had expanded, our ability to apply this knowledge has diminished (exponentially?).

EXAMPLES

  1. land clearing
  2. creating health risks
  3. DDT and other chemicals
  4. Aliens

PROBLEMS

  1. Fundamentalism
  2. Lack of understanding of spatial and temporal scales
  3. Dislocation and the “new ethics”

Ecological study must recognise all levels and approaches as facets of an extremely complex and critical important SCIENCE. To study ecology there must be some common theme - and many text books use different models/themes. I will attempt to follow a mechanistic theme i.e. that natural selection and evolution explains most of the patterns and complexity of the diversity of life. Your comprehension will be greatly enhanced by field observation and study – your own experience. BUT this is a seven week course so by definition this course can do little more than scratch the surface.

2. The order of the Natural World

The Greek for house is “oikos”, our immediate environment. Today “ecology” denotes the study of the natural environment, particularly the inter-relationships between organisms and their surroundings. AND the environment of each organism has different physical attributes, even though several may live in a single location. Different environments have different stresses.

Ecologists are interested in patterns in nature beyond those embodied in organisms – the diversity and complexity of species assemblages, energy and nutrient flows, the structure and function of systems, etc. AND ecologists explain the patterns observed.

BUT first one must see the patterns, and pose the right scientific research questions! Hence our fist practical at Kirstenbosch.

The Natural World is diverse and complex: EXAMPLES Erica spp., beetles, leaf shapes and sizes, etc.

The natural world is dynamic, but it is also stable and self-replenishing: EXAMPLES deaths comes in different ways to different species and even the same organisms (age, predators, parasites, etc.), stable systems are in fact constantly turning over and nutrients are being recycled, and populations that could be huge are not.

Man is very much an integral part of the Natural World:EXAMPLE We have had a major global impact and are continuing to do so. Stripped of our CULTURE we are a most unimpressive species. Yet today we control and manipulate nature, BUT do not control the natural physical forces – will that ever happen?

3. How we perceive and understand our environment

As we embark on a new discipline we need to take stock.

The organism is the fundamental unit of ecology. These are usually well defined units/entities, with a physical boundary from the rest of the world. Organisms are controlled by a system of internal controls that maintain an intimate and dynamic relationship with the environment. The population is a collection of similar entities, and social behaviour confers a structure on the population.

Communities embrace diverse species, but communities lack the discreetness and organisation of organisms.

Organisms fall into natural groups we call species. These are recognised according to their similarities and today can be genetically confirmed. Taxonomists are those that do the classification.

Organisms are well designed with respect to their environments. Birds have wings, lions have sharp teeth and cows have broad teeth. Design impacts other adaptations too. But as a whole the species morphology is a well integrated entity.

The natural world can be conceived as a set of patterns. We constantly recognise patterns in our surroundings, organisation and interrelationships in the complexity that surrounds us. Some are able to do this better that others, and as ecologists we have to develop and hone these skills. We are able to recognise these patterns because of the predictability of their elements. So we can ANTICIPATE NATURE FROM PAST EXPERIENCE. The more accurately we are able to predict/anticipate the better the ecologists we become.

THE PHYSICAL ENVIRONMENT

4. Life and the physical environment

We often contrast living (biotic) and non-living (abiotic) as opposites. Although these realms of the natural world are mostly readily distinguishable, they do not exist one apart from the other. Life is dependent on the physical world, but the impact of life on the physical world is mostly more subtle.

Yet the biotic and abiotic worlds are interdependent, and life (and the occurrence/distribution of organisms is dependent upon the physical world). And life is like an internal combustion engine transforming energy to perform work – the difference between the two is that in the physical world the energy level throughout the system always follows the path of least resistance. While in biological systems energy is used purposefully by the organism to maintain itself OUT OF EQUILIBRIUM with the physical forces of gravity, heat flow, diffusion, and chemical reaction (e.g. a boulder rolling downhill versus a bird flying). In the living world the ultimate source of energy is sunlight, and REPRODUCTION is uniquely a biological function.

The biotic and abiotic parts of an ecosystem are linked by a constant exchange of material through NUTRIENT CYCLES - driven by the energy from the sun. Thus the earth is a giant “heat machine”. And the variation of solar radiation with latitude creates major global patterns in temperature and rainfall.

5. Soil development

We tend to take the dirt under our feet for granted. This is VERY UNWISE, as most of the vital mineral exchange between the biosphere and the inorganic world occurs in the soil.

As with climate, soil formation is determined by physical and chemical processes with a huge variety of results dependent on local conditions (which effect rate of formation, and kind of soils formed). Soils both influence vegetation types, AND vegetation types also influence soil types (e.g. podsolisation). HOWEVER, the most important factor determining soil type is parent material (both its physical and chemical composition, and the latter affects pH - namely hydrogen ion concentration which is a key factor that mobilises cations).

Basically there are two rock types – volcanic and/or sedimentary that weather to form different soil types. AND different soil types have different water holding capacities, and different soil-air space capacities (e.g. capillarity and/or colloidal differences, the processes of calcification and salanisation occur when evaporation exceeds percolation, etc.).

  • Thus clays are formed from rocks that are fine grained (shales, mudstones, etc.), or from granites and other rocks of volcanic origin that are rich in clay minerals (mostly aluminosilicates - with K+ and Mg++ - that weather into fine particles that are ionically charged – forming lattice clay structures).
  • Sands are coarse-grained soils high in silica.
  • Silts are particles intermediate between clay and sand.
  • Loams are a mixture of clays and sands.
  • Limestones have high CaCO3.
  • Podsols are humic soils.
  • Laterites are iron (Fe3+) rich soils that were formed under wet tropical conditions.

Once formed soils remain in a dynamic state due to physico-chemical and biotic influences (and THE most important agents of change are the soil fauna and decomposers/detritovores).

NOTE: Not all soils are formed in situ, as they can be transported by wind (aeolian), water (alluvium) and gravity (colluvium) – and today by people (manuport).

6. The diversity of natural communities

Humans are orderly and we have classified animals and plants, and ecosystems/vegetation types.

Thus vegetation has been classified on

  1. Floristics: i.e. species - following different approaches such as
  2. Floral Kingdoms globally (e.g. Good), and
  3. Regionally using the techniques evolved by the Zurich-Montpellier phytosociological school
  4. Acocks (1953) for SA using his Veld Types map (1949)
  5. Structure, such as forests, woodlands, grasslands, etc.
  6. Structure and function, based on criteria such as leaf-size, sclerophylly, plant part shedding strategies, etc. and sometimes represented by Dansereau and/or Raunkiaer’s scheme
  7. Holdridge’s classification by temperature and rainfall.

ADAPTATION

7. Environment and adaptation

All organisms encounter a wide variety of environmental conditions and patterns - from a huge variety of sources/pressures that are physical, chemical and biotic (plus human). These factors all impact the structure and function of individuals, populations, communities, ecosystems and the biosphere. Some local examples for individual species (i - iv), populations (v - vi), communities (vii - viii), ecosystems (ix - xii) and biosphere (global warming) are:

INDIVIDUALS

i.Some fire survival strategies of fynbos species

  • Reseeders – e.g. Protea lepidocarpodendron and Leucospermum conocarpodendron
  • Resprouters - e.g. Protea nitida and Hypodiscus aristata

ii.Some rooting strategies for the low available plant nutrients in the heathland soils

  • Proteoid and restioid roots
  • Mycorrhizal infections – endo-, ecto- and vesicular-arbuscular

iii.The breeding strategy of the long-tailed sugarbird

iv.Fynbos ants and myrmecochory

POPULATIONS

v.Baboons social structures have evolved to allow them to survive under the harshest of conditions – predator avoidance, and troop structure with an alpha male, role of females and how young are taught

vi.Hyrax and Black Eagles

COMMUNITIES

vii.Heathlands – sclerophylly, leaf anatomy (morphological and/or functional) iso-bilateral, size, pollination syndromes, seed dispersal mechanisms, etc.

viii.Forests – quasi-organism with “own” species composition, fleshy fruits, etc.

ECOSYSTEMS

ix.Succulent Karoo

xii.Renosterveld, etc.

8. Natural selection and design in nature

The close correspondence between an organism and its environment is no accident. Only those organisms well suited to their environments survive (survival of the fittest by natural selection - Darwin), and these traits have evolved over evolutionary time. Examples:

  • Darwin’s finches on Galápagos…
  • Savanna ecosystems, and the consumers of plant productivity by invertebrates and mammals - their population structure and inter-relationships along the trophic chain/food web; grazers/browsers, carnivores/scavengers, decomposers, etc., and fire as the ultimate primary consumer.
  • Cryptic colouration and the evolution of melanistic forms of the peppered moth in the UK.
  • Cultivated plants and domesticated animals.

9. The nature of adaptation

The diverse environments globally have resulted in a vast array of adaptations from those animals in the deep ocean trenches, to mountain top communities, to deserts and wetlands. All adaptations must be integrated

  • The shape of a bird’s beak closely corresponds to what it eats, etc.
  • Legs of mammals have other functions than locomotion – such as grooming, scratching, fighting, etc. (e.g. zebras cannot scratch, so have evolved a special type of tail to swish, and a skin that can be shaken vigorously by underlying muscles)
  • Spelaeogriphus lepidops and cave crickets

The questions that are raised about the nature of adaptations are:

i.Are all species well adapted?

Successful populations are by definition successful. However, evolution is not forward looking and natural selection cannot anticipate, so human induced changes are causing havoc as they are occurring so rapidly.

ii.Adaptation can never be perfected

Because in every new population there are unfit heredity traits, and evolution is opportunistic. Because the environment is continually changing populations have to continually re-adjust.

iii.Who measures fitness?

Survival.

iv.Cultural changes is analogous to genetic evolution

These are passed through teaching and learning that parallel/supplement evolution

ORGANISMS IN THEIR PHYSICAL ENVIRONMENTS

10. Basic properties and the requirements of life

Life is an extension of the physical world so has to obey physical and chemical constraints of water, energy and nutrients (C, H, N, O and others too). AND a basic requirement of life is that it maintains the organism OUT OF EQUILIBRIUM WITH THE OUTSIDE WORLD. This comes at an energetic cost.

WATER A KEY RESOURCE

For example:

  • Terrestrial animals obtain oxygen from the atmosphere and at the same time have to guard against loss of water
  • Marine fish drink water, and have to pump out the excess salt to maintain their ionic balance so important to their existence (osmo-regulation)

Life processes take place in an aqueous medium – all organisms are composed mostly of water! And the unique physical and chemical properties of water are the basis of life (heat, liquid, change in density at 40C [so ice forms on top of water], and it is a universal solvent [NaCl in water goes to Na+ and Cl- in a reversible equation]).

NUTRIENTS FOR LIFE

Life depends on the availability of inorganic nutrients, and a wide variety is required. Firstly there are the macro elements of H, O and C (obtained from photosynthesis and the basis of sugars/carbohydrates), and N, P, S, K, Ca, Na, Mg and Fe (from the soil). The other elements required are considered to be microelements.

Table. Major nutrients and their functions (micronutrients are elements such as Co, Cu, Mo, Zn, etc.)

ELEMENT / FUNCTION
N / Structural component of proteins/nucleic acids
P / Structural component of nucleic acids, phospholipids and bone
K / Major solute in animal cells
S / Structural component of many proteins
Ca / Regulator of cell membrane permeability, structural component of bone/cell walls
Na / Major solute in extracellular fluids of animals
Mg / Structural component of chlorophyll and many enzymes
Fe / Structural component of haemoglobin and many enzymes

LIGHT - THE ENERGY DRIVING FORCE

Green plants are the primary source of energy capture by photosynthesis. The oxygen released in the process is a further key to life as we know it. Not all light is useful in photosynthesis nor is all the light visible (different wave lengths are epitomised by rainbows), and at the ultra-violet end it is damaging and at the infrared end it is warming (the role of the atmosphere and ozone).

OXYGEN AVAILABILITY LIMITS BIOLOGICAL ACTIVITY

Respiration is a key metabolic process that enables stored energy to be released. So systems depleted of oxygen become anaerobic/anoxic and metabolism can cease (blood, water, soil air space system, etc.). Organisms have specially adapted organs for oxygen capture (gills, lungs, root hairs, etc.).

Metabolism and size, also heat and size, etc.

11. Aquatic and terrestrial environments

Life evolved in the sea, and the colonisation of the land was a massive step (took hundreds of millions of years). Today terrestrial life has attained a higher degree of organic diversity. In fact it seems that the more harsh the environment the more diverse the life (cf. coral reefs and the Benguela up-welling system, heathlands and non-heathlands [e.g. fynbos and forest at Kirstenbosch]).

To contrast the aquatic and terrestrial environments we need compare the properties of water and air! They differ in

  • Buoyancy and viscosity
  • Light is attenuated very quickly in water (so photosynthesis is limited to 10m where 50% of light penetrates, and only 7% to 100m)
  • Oxygen is usually much more scarce in water
  • Water loss is a critical problem for terrestrial organisms and there are many adaptations that both animals and plants have evolved to minimise water loss

12. Regulation and homeostasis

A changing external environment is the norm. There are annual, diurnal and unpredictable cycles of change that have to be survived to thrive. Organisms respond to these cycles in many different ways – we shiver in the cold, sweat in the heat and get sun-tanned, etc. All these responses are directed towards maintaining an optimum functional level (=homeostasis). How effectively organism’s respond is about how effective they are able to regulate their metabolism to maintain homoeostasis. Responses are about costs and benefits, and the better able organisms are to regulate themselves the more efficient they are. These are essentially ecophysiological responses and are better dealt with in a course of ecophysiology, than to take up too much time in this seven-week course in ecology