Chapter2 : Natural Ecosystems Dr. Mohammad Ajjour

1. Chapter2 : Natural EcosystemsDr. Mohammad Ajjour Lect 7+ 8 University Of Palestine 2009,

2. Ecosystems • Habitat : is where an organism lives • Natural Ecosystem : a group of organism living in a area and interact with each other and with the a biotic elements in a form that they continue their existence and survival. It is a community of living organisms interacting with the abiotic surrounding through exchange of matters and energy • Ecosystems vary in size. They can be as small as a puddle or as large as the Earth itself. Any group of living and nonliving things interacting with each other can be considered as an ecosystem. University Of Palestine 2009, Dr. Mohammed Ajjour

3. Cont. Natural Ecosystem • Ecosystems differ in size, species and abiotic components , borders and time. • Constituents of Ecosystem : are either • Biotic like trees, animals , bacteria , insects…and • abiotic : like humidity , temperature, radiation, minerals. topography. Both biotic and abiotic components affect each other ( interactions ).

4. Cont. Natural Ecosystem • Ecosystems are not isolated from one another. One system blends into the next through a transitional region

5. Biotic community • Species –the unit of biotic community, it includes all organisms genetically similar enough to breed and to produce living fertile offspring in nature. A species is composed of many ( millions ) of individuals • Population - All members of a species that live in the same area at the same time. • Biol. Community :All populations living and interacting in an area. A community is made up of all the populations of organisms living and interacting with each other in a particular habitat. University Of Palestine 2009, Dr. Mohammed Ajjour

6. Biomes • Biomes -Areas sharing similar climate,topographic and soil conditions, and roughly comparable communities. Temp. and Precipitation are among the most important determinants in biome distribution. Tropical forest and desert are example of biomes. • Biosphere includes all biomes on and below the earth and above. It is a super ecosystem

7. Biotic structure of ecosystems • Although different in many ways, ecosystems are similar in the biotic structure, which is depends on feed ( trophic ) relationships between members of the system. An Ecosystem contains 3 kinds of organisms connected to each other : • Producers :plants or algae that are able to produce their food through photosynthesis ( autotrophs ) Fig

8. Energy flow through the Ecosystem University Of Palestine 2009, Dr. Mohammed Ajjour

9. Cont. Biotic structure of ecosystems • Consumers : are not able to produce their food themselves and depend on products of others or feed on themselves ( heterotrophs) . Primary consumers : feed directly on the products ( called : Grass Eaters, or hrbevores like some Insects and Elephants ), Secondary consumers eat and depend on primary consumers. There are third and fourth order consumers and more. Human can be primary , secondary or tertiary or on higher level consumer

10. Cont. Biotic structure of ecosystems • The Meat Eaters are called Carnivores , or predators, and consumers on plant and animals together are called omnivores . Parasites can be plants or animals living in or on hosts for some time without killing it directly (why ) 3. Detritus feeders and Decomposers : • Detritus feeders :feed on dead plant materials, animal wastes and cadavers like earth worm, Termites . They are either primary or secondary feeders. • Decomposers : are species of Bacteria and Fungi which feed in plant and animal rests after rotting it through their digestive Enzymes • Decomposers recycle organic matter and bring it back to its origin and play so with a very important environmental role ( How )

11. Food Chain, Food Web • All living things need food to give them the energy to grow and move. A food chain shows how each living thing gets its food. The arrow means "is eaten by".A food web shows the many different paths plants and animals are connected . • all chains and webs start with producers and end up with decomposers

12. Trophic Levels Trophic levels: successive trophic relationships in a food chain or web All producers belong to the first trophic level. All herbivores (primary consumers) are on the second trophic level.All primary carnivores (secondary consumers) are on the third level. Limitations on the transfer of energy between trophic levels creates the biomass pyramid. University Of Palestine 2009, Dr. Mohammed Ajjour

13. Ecological ( Biomass / Numbers ) Pyramid On average, 10% of the energy from one trophic level moves to the next trophic level. Because so little energy can be transferred between trophic levels, it is necessary that the first trophic level contain the greatest number of organisms, and the subsequent trophic levels contain fewer and fewer organisms. University Of Palestine 2009, Dr. Mohammed Ajjour

14. Ecological (Energy) pyramid The Energy pyramid indicates the total amount of energy present in each trophic level. It also shows the loss of energy from one trophic level to the next. An energy pyramid shows clearly that the energy transfer from one trophic level to the next is accompanied by a decrease due to waste and the conversion of potential energy into kinetic energy and heat energy.. If organisms (humans) eat high on the biomass pyramid (trophic levels 3, 4, 5, etc.),then fewer organisms can be supported than if organisms eat lower on the pyramid. University Of Palestine 2009, Dr. Mohammed Ajjour

15. At the end , after death of producers and consumers , the decomposers feed on the remaining biomass and transfer its constituents to the original primary forms and elements , which are released into the surrounding and move to the soil , seas, oceans …where it may be used again by the producers. Red arrow = energy. Blue arrow = minerals. Braun arrows = both

16. Non- feeding relationships There are other than feeding (trophic) relationship between organisms. These relationships take different forms: Mutualism exists when both partners benefit (ex. : flower x pee). Symbiosis : is a necessary mutualism for both partners ( Lichen X fungi ). Some competition take place when partners share the same habitat or have the same type of life requirements ( plants x weeds ). In nature organisms share their habitat usually without competition, because of different Niches ( where , how , when , what the organism eat and where and how they nest or sleep or breed ) University Of Palestine 2009, Dr. Mohammed Ajjour

17. Abiotic Factors Living organisms on soil are affected by many abiotic factors, such as temp., pH , humidity , light , wind topography, nutrients...... etc. In sea water salinity, mineral contents, temp. deepness ( light intensity )... etc are important . These factors affect both quality of life and geographical distribution of species. University Of Palestine 2009, Dr. Mohammed Ajjour

18. Optimal range, Zones of stress and tolerance Each species has its own favourable abiotic factors for life, which are different between species. University Of Palestine 2009, Dr. Mohammed Ajjour

19. Zones of stress and tolerance Optimum describes the best condition ,maximum,and minimum describes the limit s of tolerance, when a factor is available in far less or far more range. The limits of stress are between the Optimal Range and the limits of tolerance . Law of limiting Factors : A limiting Factor is one chemical ( macro or microelement) , biological ( weeds or predator) or physical factor ( water for plants )which limits the growth of organism even when other factors are available . University Of Palestine 2009, Dr. Mohammed Ajjour

20. Factors that affect the origin and development of Ecosystems 1.Climate : the average temp. and humidity over time . Humidity and temperature are of specific importance that affect ecosystem and its components Origin and development of Ecosystems University Of Palestine 2009, Dr. Mohammed Ajjour

21. Origin of Ecosystems 2. Microclimate : depends on - Light Intensity:south-facing versus north-facing , Soil Type,pH ,Salinity, Sand, clay, silt4.Topography 3.Biotic Factors :1. Shading of One Plant by Another .2. Chemical Produced by One Plant May Limit Growth of Another Plant.3. Presence of Herbivores  tasty plants are consumed first. 4.Physical Barriers University Of Palestine 2009, Dr. Mohammed Ajjour

22. Ecosystems in/ out of Balance Despite competitive relationship between organisms in a habitat and producer x consumer trophic behaviour , species succeed to survive in nature and to live together over time . ( how )and (why ) 1-Biotc potential : The number of a population is limited by many factors, such as Biotic potential ( number of children ,eggs , seeds , pollen grains.. ) recruitment ( ability of young offspring to survive ) , Migration to other habitat or dispersal of seeds , ability to adapt to new habitat , and resistance to diseases . University Of Palestine 2009, Dr. Mohammed Ajjour

23. Cont.Ecosystems in/ out of Balance 2- Environmental resistance : which includes biotic factors ( predators, parasites , .. ) and abiotic ( scarcity of food, temp., pH, salinity..) -Density Dependent: Mortality rates increases as the density of population increases ( Disease, Stress, Predation ) - Density-Independent Factors (Abiotic condition ) University Of Palestine 2009, Dr. Mohammed Ajjour

24. Ecological succession Ecosystyms are from time to time subjected to natural changes or disturbances ( floods, fires ) or man-made (deforestation, mining.. ). These are overcome by Ecological succession ( the gradual change from a specific biotic community to another) . As a result a new community replaces the first, and a third replaces the second ...and so on (see example) . It occurs because of the changes in the habitat . University Of Palestine 2009, Dr. Mohammed Ajjour

25. Cont. Ecological succession Two types of successions are distinguished : 1. Primary succession occurs when initial invaders ( pioneers) species occupy unoccupied land to the first time . University Of Palestine 2009, Dr. Mohammed Ajjour

26. Cont. Ecological succession A Secondary succession occurs when the plant cover in an area is removed and new species occupy the land . This change takes place gradually , not suddenly. Ecological succession is not endless . After years or decades communities in the ecosystem get more stable ( climax communities) . At this stage a Climax Ecosystem is achieved which is characterized by a) being highly resistant to adverse conditions b) high species diversity c )richness in organic matter d)shows high degree of regularity . University Of Palestine 2009, Dr. Mohammed Ajjour

27. Earth Biomes A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that environment. The climate and geography of a region determines what type of biome can exist in that region.. University Of Palestine 2009, Dr. Mohammed Ajjour

28. Biomes • Biomes are "the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment" • Biomes are classified into : Aquatic DesertsForests Grasslands Tundra • Biomes have changed and moved many times during the history of life on Earth. More recently, human activities have drastically altered these communities. Tundra Grasslands University Of Palestine 2009, Dr. Mohammed Ajjour

29. Earth Biomes Each biome consists of many ecosystems whose communities ( plants, animals , insects ..etc. have adapted to the small differences in climate and the environment inside the biome. University Of Palestine 2009, Dr. Mohammed Ajjour

30. Earth Biomes (Examples) 1. Tropical Rain Forests: A tropical rainforest is an ecosystemusually found around the equator. Minimum normal annual rainfall between 1,750 mm and 2,000 mm. Mean monthly temperatures exceed 18 °C during all months of the year . Rainforests are home to half of all the living animal and plant species on the planet. Tall, broad-leaved evergreen trees are the dominant plants University Of Palestine 2009, Dr. Mohammed Ajjour

31. Cont.Tropical Rain Forests • TR forests are called the "world's largest pharmacy" because over one-quarter of modern medicines originate from its plants. The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level and consists of shade tolerant shrubs.TRF is the habitat of many thousands of animal species and insects University Of Palestine 2009, Dr. Mohammed Ajjour

32. Cont . Tropical Rain Forests Tropical rainforests are unable to support human populations. Food resources within the forest are extremely dispersed due to the high biological diversity and what food does exist is largely restricted to the canopy and requires considerable energy to obtain. Some area were converted to agriculture ( coffee production, ..) not without many problems ( explanation ) . Soil is thick but acidic ( pH around 4 ) and poor in nutrients , due to high consumption by trees . TRF is an attractive site for environmental tourism. University Of Palestine 2009, Dr. Mohammed Ajjour

33. Earth Biomes 2-Deserts deserts occupy between one-third and one-fifth of the earth's land surface. It is an areas that receives less than 250 mm of average annual rainfall.  Some places have no recorded rainfall at all.  When it does rain, the total annual amount often comes as one sudden storm , temp. of less significance: the Antarctic, with winter mean tempe. of minus 30o C , is a true desert.  On the other extreme, tempe. in the Lybian Sahara reach 58o C, with soil surface temperatures recorded as high as 80o C. University Of Palestine 2009, Dr. Mohammed Ajjour

34. Earth Biomes 2-Deserts • In contrast to popular believe, sand is not the common surface layer in deserts.  Most often small rocks, pebbles and loose gravel make up this layer, or occasionally just bare rock. Succalent shrubs University Of Palestine 2009, Dr. Mohammed Ajjour

35. Earth Biomes 2-Deserts • Most deserts have a considerable amount of specialized vegetation, as well as specialized vertebrate and invertebrate animals. Soils often have abundant nutrients , need only water to become very productive , and have little or no organic matter. There are relatively few large mammals, such as camels , because most are not capable of storing sufficient water and withstanding the heat. Reptiles, insects and birds are common University Of Palestine 2009, Dr. Mohammed Ajjour