Ecology 1 PDF

# Ecology - Study of how organisms relate to one another and their environment - The scientific study of interactions that determine distribution and abundance of organisms - Word created by Ernest Haeckel (1869) - Predict ecological communities change over temporal and spatial periods...

# Ecology - Study of how organisms relate to one another and their environment - The scientific study of interactions that determine distribution and abundance of organisms - Word created by Ernest Haeckel (1869) - Predict ecological communities change over temporal and spatial periods - Study of relationship between an organism and its environment - Integrates all fields of biology - Environment = abiotic factors - Other organisms = biotic factors → behaviour, distributions, competition and predation # Environmental Challenge - Environments vary in relative abundance of basic resources for life. - Influenced by where you are on Earth. - Factors affected by climate: - Nutrients: construction of living tissue. - Energy: powers construction. - Water: solvent for metabolic reactions - Favourable temperature: For metabolism (optimum temperature) # Climate - Overall patterns that prevail from year to year - Driven by solar energy, Earth's rotation, and its orbit around the Sun - Shapes character of the ecosystem # Relationship Between Earth and Sun - Earth slanted by 23.5° - Solar radiation at the equator = 90° - Solar radiation has more influences in the hemisphere - Temperature between fluctuations are not big - Northern Hemisphere has large differences between temperatures, more ocean bodies in the Southern Hemisphere - Ocean: good store of energy # Seasonal Variation - Northern Hemisphere receives maximum illumination on June solstice (around 22 June) --> the sun shines directly over the tropic of Cancer. - Southern Hemisphere receives maximum illumination on December solstice (around 22 December) --> the sun shines directly over the tropic of Capricorn. - Only the tropics ever receive solar radiation from directly overhead. - Tropical regions experience seasonal changes in temperature and day length: - Temperature is high - Days last about 12 hours all year. # Temperature Varies With Latitude - Variation in months means certain mammals go into hibernation. # Torpor in Hummingbirds - Response to daily temperature variations - Temporary dormant state - When environmental temperature drops --> small endotherms (like hummingbirds) lose heat faster than they can generate it - Risks total depletion of energy - Eulampis, the West Indian Hummingbird, becomes torpid at night and lowers body temperature from 40°C to 20°C which reduces energy consumption by 80% - Less energy wastage - Prevents thermal shock # Variation Due to Atmospheric Circulation Patterns - 3 Distinct wind cells: Hadley cells, Ferrell cells, and polar cells --> divide troposphere into regions of closed wind circulations. - Heat from the equator sinks around 30° latitude where Hadley cells end. - Results in warm air not reaching the poles. # Trade Winds - Easterly winds that blow between the equator and horse latitudes. - From the northeast in the Northern hemisphere, and from the southeast in the Southern Hemisphere - Named "trade" from middle English word --> recognition of direction (18th century) of commerce trade between England's merchant fleet crossing the Atlantic. # Hadley Cells - Low latitude overturning circulations that have air rising at the equator and air sinking at around 30° latitude. - Responsible for trade winds in tropics and control low latitude weather patterns. - Responsible for environmental differences - Solar radiation --> energizes water vapour --> vapour forces hot air to go into the atmosphere --> air is replaced by cold air. -Continuous cycle between hot and cold water - Influences precipitation pattern on Earth's surface - Warm air contains more water vapour. - Equator --> air becomes warmed + absorbs more moisture from the ocean. - Warm, moist air expands as it moves upwards --> results in heat energy to dissipate across large volume. - Results in reduction of air temperature - Adiabatic cooling: reduction of temperature without loss of heat energy - Results in water released as rain - Reason why rainfall around the equator is high - Air moving towards poles in the upper atmosphere conserves its axial angular momentum - Surface air moving towards the equator is slowed down by friction # Coriolis Effect - When air/wind is deflected due to the rotation of the Earth on its axis # Variation in Rainfall - Earth's surface in not uniform. - Presence of sea currents different in temp. - Hot ocean currents from equator to polar regions (vice versa for cold) # Latitude vs Altitude - Reason for permanent snow covered mountains. - Similar biomes occur that match altitudes. - Temperature drops 6° every 1000m increase --> matched by 880km move in latitude # Coastal Regions: Rain Shadow Effect - Mountains influence weather patterns. - Warm air absorbs moisture from oceans and moves across. - Mountain stops rain clouds from going out. - Once precipitation starts to form --> clouds can move over and cross mountain. - Clouds = dry - Once they move across --> take Moisture away from environment and cause desert environment. # Combination of Factors Influence Presence of Certain Biomes - E.g. Deserts: - At 30° N + S of equator --> dry air decents because of atmospheric circulation - Next to coast line of continents --> cold ocean currents run parallel - In interior of continents --> high mountain ranges result in rain shadow effects # Coastal Regions - Currents running along seacoasts moderate temperature over nearby land. - Breeze blows from sea towards land in the day, and opposite at night. - Local effects sometimes override latitudinal variations in temperature - Continental climate: not moderated by distant oceans - Maritime climate: affected by winds that cross nearby currents - Temperature differences between land and ocean currents --> affect moisture conditions # Biomes - Climatically delineated assemblages of organisms that have characteristic appearance + that are distributed over wide land area. - Similar types of organisms and are organised into communities. - Forces convergent evolution to occur. - Organisms evolve to survive these specific environments. - South Africa = Mediterranean vegetation/fynbos. # Ocean Currents - Water expands as it warms --> sea level is about 8cm higher at the equator than at the poles. - Causes surface water to move in response to gravity - Trade winds and temperature westerlies contribute to mass flow of water at the ocean surface. - Surface water flows in direction of prevailing winds --> forming major currents - Earth's rotation, position of landmasses, and shape of ocean basins influences their movement. - Trade winds push ocean currents away from the equator. - Warm water flows away from the equator - Warm eastern side: moves east to west - Cold currents continuously replace warm currents are the equator - Warm ocean currents: faster + shallow - Cold ocean currents: not as shallow # Climograph - Shows distinction between different biomes and how their weather patterns affect them. - No biomes in very high precipitation zones. - Know where these biomes are found on Earth. # Tropical Rain Forests - Distributed around the equator equally - Very wet and humid - Half of terrestrial life occurs in the rain forest. - Keystone species: one species is essential for the survival of many other species - E.g. Fig trees --> enables survival of many animals. # Types of Tropical Rain Forests - Tropical rain forests: - Grow where annual rainfall exceeds 250cm - Mean temperature is at least 25°C and humidity is above 80% - Highly diverse habitats with a dense canopy - High rates of productivity and decomposition - Tropical deciduous forests: - Occur where winter drought reduces photosynthesis and most trees drop their leaves. - Along the equator - Heavy rain season and long dry seasons - Monsoons - Tropical montane forests/cloud forests: - Occur at high altitudes in tropics - Productivity is limited by low temperature, high humidity, and sunlight blocking clouds. - Mainly found in Asia - Cloudy and misty environment - Quite cold - Epiphytes can dominate # Africa Tropical Rainforests - Drier than ones in South America. - Different niches within the canopy - Mammals # Asia Tropical Rainforests - Mixture of emigrants --> species grow out of water. - Increases precipitation - Epiphytes --> grow on rocks, trees and are parasites - Have flying animals --> spread body surface and glide through the air. # South America Neotropics Tropical Rainforests - New area - Animals look similar - Similar niches # Savannas - Bordering tropical rain forests - Grasslands with few trees - Found in areas adjacent to tropical deciduous forests. - Grasses grow in the rainy season and die back during dry seasons (may last 8/9 months) - Africa savannas --> large herbivores, mammals and predators - Seasonal rainfall. - First dominated North America - Shift of biomes --> led to extinction of megaherbivores - Dust plays role in increasing biomes # Deserts - Rainfall averages less than 25 cm/yr. - Hot deserts occur near 30° latitude. - Descending air masses create very dry conditions. - Cool deserts form in rain shadows at higher latitudes. - On west coasts with cool currents - Rainfall is infrequent, heavy and brief. - Runoff erodes topsoil --> high in minerals and low in organic matter. - Sparse vegetation's --> water conserving adaptations, trees with long taproots and short lived annuals. - Abundant small animals --> live in burrows and are nocturnal. - Adaptations to conserve water and energy. # Chaparral - Most species function the same in all these biomes. - Scrubby mix of short trees and low shrubs. - Dominates narrow sections of the coastal land between 30°-40° latitude - Winters are cool and wet - Summers hot and dry - Rainfall: 25-60 cm per year - Dense shrubs with hard, tough and evergreen leaves - Most plants are dormant during hot, dry summers - Lightning sparks fires --> adaptations to fire. - Some species release seeds from fire resistant cones or pods and seedlings grow in ash-enriched soils. # Temperate Grasslands - Include prairies of North America, steppes of central Asia, pampas of South America, and veldt of Southern Africa - Extend across interiors continents - Winters are cold and snowy - Summers are warm and dry - Grasses effective in absorbing CO2 - Highly productive --> can survive under large mammals # Temperate Deciduous Forests - Grow at low mid-altitudes with warm summers, cold winters, and annual precipitation between 75-250cm. - Most plants shed leaves in the winter and grow new ones in the spring. - Decomposition enriches soil. - Trees form a canopy over woody shrubs, herbaceous plants, and ground layer mosses or liverworts. - Farmers, insects, and introduced diseases have nearly eliminated some dominant species. - Large mammal populations have declines and small mammals predominate. # Taiga-Evergreen Coniferous Forests - Boreal forests is a circumpolar expanse of evergreen coniferous trees in Europe, Asia, and North America. - Very cold winters. - Precipitation during short summers. - Dominated by white spruce and balsam fir --> fallen needles acidify soil which speeds leaching of nutrients. - Fewer shrubs and herbaceous plants grow beneath conifers. - Peat mosses, shrubs, and stunted trees dominate acidic bogs called muskegs - Native animals --> herbivores, carnivores, small mammals, mosquitoes, black flies, and gnats. - Fires: 70-100 years # Tundra - Treeless arctic tundra --> from boreal forests to polar ice caps in Europe, Asia, and North America. - Only the topmost layer of soil ever thaws --> ground below (permafrost) is impermeable and permanently waterlogged forming bogs. - Anaerobic conditions - Low temperature slows decomposition. - Wet detritus accumulates. - Plants include low growing lichens, mosses, grasses, perennial herbs, dwarf shrubs and few stunted trees. - Some small mammals and birds --> permanent - Large herbivores and birds --> migratory - No trees --> strong winds. # Alpine Tundra - Occurs on high mountaintops throughout the world. - Dominant plants form mats withstand strong winds. - Winter temperature --> below freezing and shaded patches of snow persist in summer. - Soil --> thin, fast-draining, and nutrient poor - Photosynthetic activity is low - High altitudes # South African Biomes - Temperature differences key aspect - Cold and warm currents - Creates different biomes across the coast. ## Biomes of South Africa - Albany Thickets - Coastal Belt - Desert - Fynbos - Grassland - Nama Karoo - Savanna - Succulent Karoo - Forest ## Cape Terminology - Cape Floral Kingdom (CFK) - Cape Floristic Region (CFR): only floristic region in CFK geographic area - Forest Biome - Nama Karoo Biomes - Succulent Karoo Biome - Thicket Biome - Fynbos/chaparral biome - Fynbos vegetation --> Proteas, Ericas, Restios - Renosterveld vegetation --> Daisies, bulbs, grasses + renosterbos ## Floral Kingdoms of the World - 6 Floral Kingdoms - South Africa --> multiple floral kingdoms - Cape floral kingdom --> only one that exists in a single country ## Cape Floral Region - Most of CFK covered by fynbos - Compare original extend of vegetation --> lots of plant life. - Very species rich --> even though it's far from the equator. - Richer than many areas of Africa - Close to the richness of the Neotropics when controlling for size. - Both fynbos and renosterveld have unique soils. ## Fynbos Biome - South western part of RSA - More than 40% rainfall in the winter - Sea level --> 2250m - Very nutrient poor soil - Frequent fires - High endemism - Diversity of species --> small selective feeders, seed eaters and bulb feeders - Plants have a low N to C ratio - Plants have hardy and taste bad - Low density of herbivores --> increase in C biomass ## Characteristics of Fynbos Soils - Determines what species will occur there. - Nutrient poor (Nitrogen + Phosphorus) - Sandstone derived - Course grained - Nutrient poor - Leeched - Poor water retention - Acidic - Shallow - Quarzitic. - Mountain habitats - Shale/granite derived - Fine grained - Intermediate nutrients - Good water retention (clay) - Deeper - Inter mountain. - Abiotic factors: - Dry summers - Strong winds - Winter rainfall - Fire dependent (5-20 year intervals, average 13 years) ## Flowers - Protea-like shrubs with large leaves - 1-3m high - Leathery leaves - 330 sp. - Erica-like plants with fine leaves - 3000 species. - 650 family Ericaceae - Reed-like Restio plants - Provides shelter for various different animals. - Bulbous plants/geophytes - Sometimes with fire-stimulated flower production. ## Species - Frog species common --> lots of vegetation which allows variation in amphibians - As increase SA --> species richness starts to increase. ## Diversity + Endemism - Diversity - Covers 90 000 km² - 8200 plant species - Endemism - 68% of species - 20% of genera - 6 endemic families - E.g. Kaapse skiereiland ## Fire - Resprout: survive fire as adults and produce new leaves and branches from protected buds. - Top of the plant burns away and bottom of the plant survives underground. - Reseeders: depend on seeds to recolonise post fire. - Most fynbos plants are reseeders. - Lots of seeds survive post fire. - Competition is lower --> parental plants don’t outcompete seedlings. - Small rodents die in fires --> don't feed on seeds so more seeds present. - Serotiny: maintainance of seeds in cones that are released post fire and spread by wind. - Ants take seeds into burrows and then germinate --> seeds are poor in nutrients. ## Seed Dispersal Through Ants - Myrmechochory: ant dispersal - 1300 species in Fynbos have elaiosomes - Elaiosomes: little green cap on the see which is made up of fatty substances that they like to eat - Most important ants: _Anoplolepis_ and _Pheidole_. - Germination is regulated by daily soil temperature fluctuations and chemical signature in fire smoke - Myrmecochory allows seeds to escape rodents and fire. ## Renosterveld - Dominated by daisy family - Renosterveld --> gave renosterveld its name. - Large diversity of grasses. - Carries a large number of animals. - Soil - Fire - Seed dispersal by wind. ## Succulent Karoo Biome (Namaqualand) - CFR --> large diversity. - Rain every year for a short time during the winter 20-290mm - Hot, dry summers. - Dominated by succulents and dwarf shrubs. - Lots of geophyte. - Endemic reptiles. - No fires --> biomass is low. - Similarity between fynbos and succulent karoo --> winter rainfall and large number of species. ## Ecology - Unusual desert flora in most are perennial with short lifespans. - High turnover. - Can't withstand long periods of dehydration or frost - Requires average rainfall. - E.g. stone plants - Plants that can only be opened if a rain droplet hits it: - Spring-like mechanism. - Once water droplets hit seeds --> disperse them over a couple of meters - Daisies germinate in the winter, flower and release seeds over a 3 month period. - High diversity of reptiles and herbivores. # Nama Karoo Biome - Central plateau --> western half of RSA - Summer rainfall: 100-520 mm. - 500-2000m above sea level - Second largest biome - Very little rainfall (seasonal) with 18 year cycles --> associated with historical migratory patterns of springbok - Plants: grasses and shrubs - Drought resistant shrubs: _Penzia incana_ (ankerkaroo) with grasses - Low no. of succulents and geophytes - _Acacia karoo_ trees in river beds - Semi-arid environment. # Savanna Biome - Well developed over lowveld, brushveld and Kalahari areas. - Delimiting environmental factors complex. - Summer rainfall: 235-1000mm --> varies a lot. - Sea level: from 2000m. - Grasslands with scattered trees - Canopy of trees --> not continuous - Largest biome --> covers 46% of the area in RSA - Tropical and sub-tropical plant growth forms - Combination of woody plants and grasses. - Very warm wet season (Oct-Apr in RSA) and average dry season. - Strong seasonality --> lead to accumulation of fine, dry and flammable material (grasses) - High, productive biomass. - Supports large herbivores and predators. - If increase in rainfall, less fire or less large animals --> trees will dominante - Fire is important!!! - Too much = grasses dominate. - Too little = trees dominate. # Grassland Biome - High lying parts of central plateau --> interior KwaZulu Natal and E. Cape. - Mainly summer rainfall: 450-1200mm - Temperature: -13 to 41°C - Sea level: from 2850m. - High altitude and temperature fluctuations. - Savanna biome without trees. - Plants: grasses and geophytes. - Frost, fire and grazing important --> prevents tree establisment. - High biodiversity. - Threats: expansion of crop farming, overgrazing, and urbanization. - C3 plants increase CO2 --> lower chance of respiration - Trees: C3 - Grasses: C4 - Increase in CO2 --> more trees and less grasses. - Trees don't dominate: herbivores eat leaves, and large mammals push over trees. - Fires: - Trees flat at the bottom --> herbivores eating bottom of leaves. - Increase moisture --> high biomass. - Difference between theoretical and actual biomass is big due to consumer control (e.g. herbivores) # Effects of Fire on Grass-Tree Dynamics - Grasses well adapted to fire --> meristematic tissue below ground - Once top part burns --> can grow again. - Trees also have meristematic tissue --> tuber - Fire --> everything above ground burns - Meristematic tissue allows grasses and trees to regerminate and grow again. - Increase fire frequency: - Grasses will reprout (always) - Trees won’t after a while --> tuber will die - More frequent fires --> less chance of trees establishing - After long intervals --> trees grow tall - Trees and leaves above fire are protected. - About 1.8m will survive and everything below will die. - Trees then grows further and there is an increase in biomass. - Trees enables stems to be protected from the environment. - Fire prevents savannas turning into forests and grasslands turning into savannas # Forest Biome - Highly fragmented. - Restricted to frost free areas - Rainfall >525mm in winter or >750mm in summer - From sea level: 2100m - High altitude - Used to be a continuous biome --> decrease in CO2 caused fragmentation and was replaced by grasslands/savannas - Continuous canopy of evergreen trees. - Ground layer almost absent --> shade - Smallest biome. - Cover <0.24% of RSA - Threat: fragmentation - Speciation - Moisture --> decrease in fires and increase in plants. - Light in limited resource - When trees fall --> creates a gap in the canopy and provides an opportunity for new seedlings - Understory sees little light --> competition between seedlings when light is present. # Thicket Biome - Not officially recognized in scientific literature. - Transition biome between forests and savannas. - Thicket replaces forests. - Protected from fires - Rainfall too low for true forests - Low trees and shrubs --> lots of bush - Few herbaceous plants - _Spekboom_ --> grows in dense thicket biome - Elephants clear spekboom and other shrubs for mammals to move through --> so animals can move from biome to biome. # Population Growth - Population: all individuals of the same species that share the same habitat and can potentially interbreed. # Population Dispersion - Populations vary in dispersion, spatial distribution of individuals within geographical range: - Random dispersion: individuals are distributed unpredictably within uniform habitat. - Clumped dispersion individuals group together due to patchy habitats, social groups and reproductive patterns. - Uniform dispersion individuals repel each other and tend to be evenly spaced because resources are in short supply. # Demography - Statistical study of changes in population size, age structure, and sex ratios. - Predict probability of population to die. - Important for management and conservation of species. - E.g. Covid-19 cases in 2020 --> exponential growth. # Exponential Growth (J curve) - Change in population over time. # Formula (ΔΝ/Δt) = dN/dt = (b − d)N - b: per capita birth rate --> number of births in a population during a specified time period divided by population size. b = B/N - d: per capita death rate --> number of deaths divided by population size during the same time period. d = D/N