Elements Of Ecology PDF

ELEMENTS OF ECOLOGY BLY 101: GENERAL BIOLOGY I  Development of Communities and Ecosystems 2  Discussion outline ❑ Succession ❑ Population Ecology ❑ Biomes  Succession 3  The dynamic nature of n...

ELEMENTS OF ECOLOGY BLY 101: GENERAL BIOLOGY I  Development of Communities and Ecosystems 2  Discussion outline ❑ Succession ❑ Population Ecology ❑ Biomes  Succession 3  The dynamic nature of natural communities enable them experience gradual and continuous change from one type to another.  Succession may be described as the natural, orderly process of community change which finally stabilizes as a mature, stable and self-maintaining community  Individual successions are known as seres and the developmental phases called seral stages  Succession 4  There are two major kinds: 1. Primary succession 2. Secondary succession  Primary Succession 5  Occurs on a bare or newly formed area, where no life has previously existed  Very slow process, taking up to hundreds of years  Common examples are plant succession that occurs on bare rock surfaces (xerosere/xeric succession)  Plant communities that may be found may occur in the following order: Pioneer species Annuals Herbaceous Shrubs Trees  Secondary Succession 6  This starts in areas previously occupied by vegetation, but has experienced alteration/denudation of environment by means of natural disasters/man-made disturbances  Is much more common in nature and the colonization period is usually faster compared to that of primary succession  The rapidity of colonization depends on germination of spores and seeds in the soil gene bank  7 TIME TIME Hundreds of years 40+ years  Climax community 8  This refers to the peak, relatively stable biotic community attained in an area after evolving through a series of succession stages  It may also be described as the most complex, diverse and productive community an area can sustain  Typical examples are tropical rainforests known for species richness and complex biotic interactions  Zonation 9  This refers to the spatial distribution of organisms in a community into distinct zones based on variations found in the physical environment  Each zone in a given area is occupied by species that can adapt to its conditions. Example includes vertical zonation on mountains with increasing altitude  Basic difference between zonation and succession is that with zonation, species vary with space (spatial), while in succession, species vary with time (temporal).  10 Mountainside zonation  11 Rocky shore zonation  Population Ecology 12  Population refers to group of individuals of a particular species occupying a definite space in which individuals interact, interbreed and exchange genetic information  Population ecology involves the study of characteristics, structure and regulation of populations  Population dynamics also describe how population size changes over time  Key Features of Populations 13  Population size: Number of individuals in a given place at a given time  Population density: Number of individuals/size of population per unit area/volume e.g. 500 mango trees per hectare, 40 lions per 100km2 , 5 million diatoms per cubic metre of water  Population Growth: Change in population size/number of individuals between two periods. Population growth rates may either be positive or negative  Key Features of Populations 14  Natality: Also called birth rate. Refers to rate of reproduction or birth per unit time. Usually expressed in percent or numbers per unit time  Mortality: Also called death rate. Number of deaths per unit time. Usually expressed in percent or numbers  Survivorship: The percentage of individuals that die before reaching reproductive age (pre-reproductive mortality) is one of the main factors affecting population size. It is more variable than birth rate in a population  Key Features of Populations 15  Survivorship: If we start with a population of newborn individuals and the number of survivors is plotted against time, a survivorship curve is obtained  Three major types of survival curves exist  Survivorship curves help us determine death rates of individuals of different ages and hence which ages they are most vulnerable. We therefore gain understanding on how population size is regulated  Growth Curves 16  Two major types exist, (a) the J-shaped growth curve and (b) the S-shaped or sigmoidal growth curve  Sigmoidal growth curve: Describes a situation in which population density of an organism in a new environment increases slowly initially,  As it adapts to new conditions and establishes, population increases rapidly approaching an exponential growth rate,  It then shows decline/declining rate of increase until a zero population growth rate is achieved (i.e. Birth rate=Death rate)  Growth Curves 17  The S-shaped/sigmoidal growth curve is typical of populations colonizing a new habitat, in which conditions of growth are ideal e.g. microorganisms growing in culture plate, grasses in grassland undergoing secondary succession  The J-shaped growth curve: Also called the boom and bust curve. It describes a situation in which, after the initial establishment phase (lag phase), population growth of species continue in an exponential form until abruptly stopped, and begins to rapidly decline (‘crash’)  This crash shows that environmental resistance (or external limiting factors) suddenly becomes effective  Growth is said to be density independent in this setting, since regulation of growth rate is not tied to population density until final crash (bust)  Growth Curves 18  The crash may be triggered by factors such as seasonality, end of a breeding phase, either of the organism itself or of an important prey species. It may also be induced by human intervention such use as pesticides, herbicides, or insecticides.  Such populations show a fluctuating recovery pattern after the bust and adjust to a new carrying capacity of the environment  Examples of this in nature are algal blooms in water bodies, whose populations are then controlled by man-made interventions.  BIOMES 19  A biome may be described as the largest geographic biotic unit which constitutes a major community of plants and animals with similar life forms and environmental conditions including climate, soil type and quality, water availability, etc.  A biome also typically includes multiple ecosystems and is usually named or classified for the dominant type of vegetation found or climatic condition prevalent in the area Examples of Biomes 20  Categories of Biomes 21 Terrestrial Biomes Aquatic  Terrestrial Biomes 22  Tropical rainforest  This biome typically occurs near the equator where rainfall is abundant and occurs throughout the year  World regions where this biome occurs are found in South and Central America, West and Equatorial Africa, South East Asia, Indonesia and North East Australia  They mostly comprise the most diverse and rich ecosystems with an abundant array of plant and animal species  Terrestrial Biomes 23  Montane forests (Cloud forests)  This biome typically occurs on highlands and tropical mountains in Africa, South America and New Guinea  Climate is usually cold and non-seasonal  Vegetation found here mostly composed of small, stunted trees with contorted branches and low canopy of broad, evergreen leaves. The tree branches are heavily covered with masses of lichens, mosses and ferns  Terrestrial Biomes 24  Tropical seasonal forests (Moist deciduous forests)  This biome occurs in humid, tropical climates with a clear, dry season where there are monsoons (high winds with heavy seasonal rainfall) with representative areas in West and East Africa, South and Central America, South East Asia and India.  Deciduous trees are the more prominent vegetation found here including teak (Tectona grandis), neem (Azadirachta indica), etc.  Terrestrial Biomes 25  Woodland (Tropical broad-leaved woodland)  This biome occurs in Northern South America, Southern Africa, West Indies and Myanmar (Southeast Asia)  Contains small trees which replace the vegetation of tropical seasonal forests when the climate gets drier and the soil poorer  Tree canopy is typically 3 – 10 meters and consists of trees or shrubs with twisted branches and thick, fire adapted bark e.g., baobab (Adansonia digitata), Albizia zygia, Annona senegalensis, etc.  Terrestrial Biomes 26  Temperate rainforest  Occurs along the Pacific coast of North America, New Zealand, Australia and Chile (South America)  Climate is cool and maritime with abundant summer rain with much cloudiness and fog. Temperature variation is low  Dominant vegetation include the redwoods (Sequoia sempervirens), mountain ash (Eucalyptus regnans), etc.  Terrestrial Biomes 27  Temperate deciduous forests  Occurs in Europe, Asia and the Americas  Experience a high degree of seasonality from cold, sub-zero winters with frost and snow to warm, mild summers that are often wet with occasional drought spells  Vegetation dominated by broad leaved deciduous trees like oak (Quercus), lime (Tilia), elms (Ulmus), maple (Acer campestre), shrub species, etc.  Terrestrial Biomes 28  Temperate evergreen forests  Occurs in world regions including northwestern parts of the United States of America, Southern Australia, Chile, the Mediterranean, and New Zealand  Occur in a variety of climates  Vegetation dominated by trees with tough, evergreen and broad, but relatively small leaves. Examples include Douglas fir, spruce, beech, etc.  Terrestrial Biomes 29  Temperate woodland  Occurs in world regions including parts of the western United States of America.  Vegetation dominated by small trees with incomplete (broken) canopy and the general appearance resembles grassland with occasional scattered trees  Pines, junipers, along with shrubs and grasses may be usually found here  Other Terrestrial Biomes 30  Temperate shrubland  Boreal grassland (Taiga)  Savannah (tropical grasslands)  Temperate grasslands (Europe steppe, North American prairie and South American pampas)  Alpine shrubland  Alpine grassland  Tundra  Desert  Aquatic Biomes 31 Wetland and Freshwater Coastal and Marine  Cool temperate bog  Marine rocky shore  Tropical freshwater  Marine rocky beach swamp forest  Mangrove swamp  Temperate freshwater  Marine mudflat swamp forest  Coral reefs  Lakes, ponds, rivers,  Temperate saltmarsh and streams  Significance of Biomes 32 Biomes help us to understand how ecosystems differ from each other Monitor changes occurring in various ecosystems It helps to estimate the productivity of the ecosystems and the effect of climatic changes on them  Significance of Biomes 33 Helps us to understand the type and significance of interactions with various plants and animals The resources, habits, and habitats are dictated by the biome an organism lives on Performs various ecological services such as acting as carbon sinks, natural resource reserves, etc. which are unique to each biome.