Chapter 2

1. Chapter 2 Abiotic Factors

2. 2.1 What is an Abiotic Factor? • The word abiotic literally means ‘non-living’. • An abiotic factor is any non-living parameter, component, aspect or factor that controls the distribution (geographic spread) and abundance (numbers of individuals) of biological organisms on Earth.

3. 2.1 What is an Abiotic Factor? • Consider planting new flowers in a garden, • Are aware of the requirements for the optimum growth of those flowers; • sunlight, water and good fertile soil. • Without these requirements (and carbon dioxide), the flower would perish.

4. 2.1 What is an Abiotic Factor? • The same concept applies for all life on the planet. • Organisms need certain abiotic factors in order to survive • even when an organism has the basic factors to survive, abiotic factors also control how well an organism lives.

5. 2.1 What is an Abiotic Factor? • Abiotic factors can be broken down into two categories; • Physical resources • Physical factors

6. 2.1 What is an Abiotic Factor? • Physical resources are those abiotic factors that an organism requires to survive. • For a plant, it is sunlight, water, carbon dioxide and nutrients (and soil to a lesser extent). • Physical resources for animals include oxygen, water and nutrients.

7. 2.1 What is an Abiotic Factor? • Physical resources are those abiotic factors that an organism requires to survive. • For animals and plants to lack any one of these physical resources means death • they are absolute resources (you are absolutely dead without oxygen).

8. 2.1 What is an Abiotic Factor? • Physical factors are those abiotic factors that limit the degree (quality) of life that can exist. • They also tend not to discriminate between plants or animals. • Examples include the pH (acid and base) of water, degree of salinity and temperature.

9. 2.1 What is an Abiotic Factor? • Physical factors are those abiotic factors that limit the degree (quality) of life that can exist. • When factors such as these determine the presence or absence (as opposed to the life or death) of a species in an environment, these factors are referred to as limiting factors.

10. 2.1 What is an Abiotic Factor? • Class Exercise 2.1 • List as many physical factors that you can think of.

11. 2.1 What is an Abiotic Factor? • Early studies by natural historians realised the importance of abiotic factors and the control they had over organisms. • Laws such as the Law of the Minimum and the Law of Tolerance have made significant inroads into our understanding of the science and effects of abiotic factors.

12. 2.1 What is an Abiotic Factor? • Liebig’s Law of the Minimum basically states that even though an organism might utilise several abiotic factors, it is often only one of these factors that is truly limiting the optimisation of the organism’s growth, and whatever this factor may be it is termed the limiting factor.

13. 2.1 What is an Abiotic Factor? • Example : the relationship between phosphorus (an important nutrient) and algal blooms in waterways. • The Experimental lakes showed conclusively you wont get an algal bloom until there is enough bio-available phosphorous • Nutrients other than phosphorus can be the limiting factor.

14. 2.1 What is an Abiotic Factor? • Tolerance was added to the law of the minimum • there are both upper and lower limits of physical factors an organism can tolerate • The most obvious example of Shelford’s Law is temperature. • No organism can live below zero, and no organism can live above 100OC (extreme examples).

15. 2.1 What is an Abiotic Factor?

16. 2.2 Water as an abiotic factor • Without doubt, all life on Earth needs water, • Water cycles through the biosphere in what is called the hydrological cycle. • This cycle is how water is transported through all of the spheres of the environment, and is also the source of waters purification process. • This cycle is immensely important in ecology • Why?

17. 2.2 Water as an abiotic factor • Freshwater is ‘distilled’ from salt water as it goes through the evaporation process in the cycle as the sun's rays cause fresh water to evaporate from sea water and the salts are left behind. • Vaporised fresh water rises into the atmosphere, cools, undergoes condensation and falls as rain over the oceans and the land, which start the whole process over again.

18. 2.2 Water as an abiotic factor • A smaller amount of water also evaporates from bodies of fresh water. • Since land dries above sea level, gravity eventually returns all fresh water to the sea, but in the meantime, it is contained within the standing water bodies such as lakes and ponds, flowing water (streams and rivers) and groundwater.

19. 2.2 Water as an abiotic factor • When rain falls, some of the water sinks or percolates into the ground and saturates the earth to a certain level. • The top of the saturation level is called the groundwater table or simply the water table. Groundwater is also sometimes located in a porous layer, called an aquifer that lies between two sloping layers of impervious rock.

20. 2.2 Water as an abiotic factor

21. 2.3 Light as an abiotic factor • Sunlight is the primary source of energy in nearly all ecosystems. • The entire food chain starts with organisms that are photosynthetic (termed primary producers), and so without sunlight, all life (excluding some microbes) dies, not just the plants.

22. 2.3 Light as an abiotic factor • Light is a form of energy of which there is a broad spectrum, called the Electro-Magnetic Spectrum (EMS). • Our light comes from the Sun which produces spectrum of light that is mainly in the form of visible light and heat (infra-red, IR), with some ultra-violet (UV) and ‘traces’ of lower energy radiation (microwaves, radiowaves etc.).

23. 2.3 Light as an abiotic factor • Light the Earth receives is used by plants in photosynthesis, and is therefore possibly the most important of all abiotic factors, • Light energy also affects other factors such as temperature through interactions with water, land and air.

24. 2.3 Light as an abiotic factor

25. 2.3 Light as an abiotic factor • Factors such as • quality of light, • intensity of light and the • length of the light period (day length) all play an important part in an ecosystem.

26. 2.3 Light as an abiotic factor • Quality of light (i.e. the colour) • Plants absorb blue and red light during photosynthesis (the green is not absorbed, which is why plants appear green!). • In terrestrial ecosystems the quality of light does not change much.

27. 2.3 Light as an abiotic factor Quality of light (i.e. the colour) • In aquatic ecosystems, both blue and red light are absorbed by water, and as a result, do not penetrate deeply into the water. • To compensate for this, some algae have additional pigments which are able to absorb other colours as well.

28. 2.3 Light as an abiotic factor • Light intensity ("strength" of light) • The intensity of the light that reaches the earth varies according to the latitude and season of the year. • The southern hemisphere receives less than 12 hours of sunlight during the period between the 21st March and the 23rd of September which is less intense than the 12 hours of sunlight during the following six months.

29. 2.3 Light as an abiotic factor • Day length (length of the light period) • Certain plants flower only during certain times of the year. • One of the reasons for this is that these plants are able to "measure" the length of the night (dark periods).

30. 2.3 Light as an abiotic factor • Other interesting light responses • Phototropism - is the directional growth of plants in response to light. • Phototaxis - is the movement of the whole organism in response to a unilateral light source • Photokinesis - Variation in intensity of locomotory activity of animals • Photonasty - Photonasty is the movement of parts of a plant in response to a light source, but the direction of the stimulus does not determine the direction of the movement of the plant.

31. 2.3 Light as an abiotic factor • The absence of light • Light requirements of plants differ and as a result distinct layers, or stratification, can be observed in an ecosystem. • Plants which grow well in bright sunlight are called heliophytes (Greek helios, sun) • and plants which grow well in shady conditions are known as sciophytes (Greek skia, shade). • Stratification is often seen in tropical rainforest with a distinctive canopy (top), mid storey and ground covering plants (understory).

32. 2.3 Light as an abiotic factor

33. 2.4 Temperature • The distribution of plants and animals is greatly influenced by extremes in temperature, for instance the difference between summer and winter, or even day and night. • As well as temporal differences, temperature is also controlled by latitude (it is colder towards the poles) and altitude (it is colder at higher altitudes).

34. 2.4 Temperature • The following are examples of temperature effects with ecosystems: • the opening of some flowers • the seed of some plants (biennials) normally germinate in the spring or summer • deciduous trees lose their leaves in winter and enter into a state of dormancy • Cold blooded and warm blooded animals • in desert conditions many cacti flower at night and are pollinated by nocturnal insects • hibernation in winter is common in reptiles and some mammals • some animals collect fat or other resources during favourable periods • seasonal movements occur in some animals (migration)

35. 2.5 Climate as an abiotic factor • Climate is the long term average of several meteorological parameters, such as rainfall, temperature, humidity and wind speed. • Differences in climates at various locations around the Earth are the primary cause of the different patterns of vegetation we see.

36. 2.5 Climate as an abiotic factor • As plants are very limited by availability of water, it makes sense that the distribution and abundance of plants is controlled by water availability, • as a result, the most important factors to consider when dealing with climate are the distribution of temperature and moisture.

37. 2.5 Climate as an abiotic factor • Significant climatic conditions that affect the ecology of an area include; • El Nino and La Nina • Mid latitude desertification • Altitude and latitude • Maritime and continental climates • Rain shadow • Slope effects

38. 2.5 Climate as an abiotic factor • Class Exercise 2.2 • Your teacher will hand out an outlined map of Australia. use the map to identify the major climatic zones in Australia. Go to www.bom.gov.au for details of the Koppen Classification of climates.

39. 2.6 Geographical/logical abiotic factors • There are several factors in this class, including altitude, latitude, longitude (to a lesser extent), and the relative position of landmass to sunlight, water catchment capacity, soil conditions and groundwater behaviour.

40. 2.6 Geographical/logical abiotic factors • Physiographic factors • the physical nature of the area, such as altitude, latitude, slope of land and the position of the area in relation to the sun or rain-bearing winds. • As mentioned, altitude plays a role in vegetations zones as nothing grows above a height of about 4000 meters. • Latitude creates similar zones and gradients as it is colder towards the poles

41. 2.6 Geographical/logical abiotic factors • Slopes are important when considering the temperature of the soil surface on land with a northern slope, on level and on land with south facing slopes. • Slopes that face the rain-bearing winds are covered with forest, whilst the slopes on the ‘dry’ side are in a rain-shadow and dry scrub is often found growing on these slopes

42. 2.6 Geographical/logical abiotic factors • Soil • The abiotic factors in soil include soil texture, soil gases, soil temperature, soil water, and soil acidity / basicity etc. • Also included is the chemicals that make up the soil (such as minerals and carbon)

43. 2.6 Geographical/logical abiotic factors • Soil texture • The size of soil particles varies from microscopic particles called clay to larger particles called sand. • Loam soil is a mixture of sand and clay • Sandy soils are suitable for growing plants because they are well aerated, • Clay soils are suitable for plant growth because they hold large quantities of water and are rich in mineral nutrients.

44. 2.6 Geographical/logical abiotic factors • Soil Gases • Soil air is found in those spaces between the soil particles that are not filled with soil water. • The amount of air in a soil depends on how firmly the soil is compacted. • In well-aerated soil at least 20% of its volume is made up of air.

45. 2.6 Geographical/logical abiotic factors • Soil temperature • Soil temperature is an important ecological factor. • It has been found that the temperature of soil below a depth of about 30cm is almost constant during the day but seasonal temperature differences do occur. • At low temperature there is little decay by decay-causing micro-organisms.

46. 2.6 Geographical/logical abiotic factors • Soil water • Soil water can be classified into three types, namely hygroscopic, capillary and gravitational water. • Hygroscopic water occurs as a thin film of water around each soil particle. • Capillary water is that water held in the small spaces between the soil particles and • gravitational water is the water which drains downwards through the soil.

47. 2.6 Geographical/logical abiotic factors • Acidity or alkalinity of soil (the pH of the soil) influences the biological activity in soil and the availability of certain minerals. • Thus the pH of soil has a greater influence on the growth and development of plants.

48. 2.6 Geographical/logical abiotic factors

49. 2.7 Physiochemical abiotic factors • This class refers to all of the physical and chemical properties of the matter of the Earth. • Includes the physical properties of water (melting points, boiling points and waters ability to dissolve certain materials) • as well as the chemical properties, such as the acid or base nature of the water.

50. 2.7 Physiochemical abiotic factors • The following parameters are considered important physiochemical abiotic factors; • pH (i.e. acidic or basic) • Surface area • Dissolved Oxygen (DO) and other dissolved gases (e.g. CO2) • Turbulence • Average wind speed • Dissolved salts (such as NaCl, or table salt, but there are many others!) • Sands, silts and clays • Temperature • Humidity