Organisms and Environments
Organisms and Environments BIOL 116
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Date Created: 10/23/15
Distribution of Organisms Terrestrial Biomes Major Terrestrial Biomes of Earth z w SA v Tropic of Equator Tropic of Capricorn lEEI Chaparra39 Cl Tundra Tmpical orm Temizerale grassland High mnumains 53mm Temperate broadleafloresl l 1 Polar ice Desert CnDVuM rum mumu Incquot pummmg s a Hitmin Cunning Coniferous forest 2 In the previous lesson you learned some of the basic characteristics of major aquatic biomes While aquatic biomes dominate the majority of Earth s surface we are generally more familiar with the terrestrial biomes In addition the terrestrial biomes likely hold even more organismal diversity than do the aquatic biomes although it is impossible to say exactly how much more as Earth s entire biological diversity may never completely be known The illustration here shows the distribution often major terrestrial biomes ranging from the warm and wet tropical forests to hot and dry deserts to the permanently frozen polar ice regions Each biome in turn represents unique challenges and opportunities to the organisms that inhabit it The Geography of Terrestrial Biomes Strongly in uenced by tem perature w and precipitation in more rapid Tempme mmruv my A nuuI quotrim xgm39pmwn m 5 uctuations in temperature Conllemu iami Amie arm um am 500 Ian Annual mun nmupiu oium a min What challenges do terrestrial biomes as opposed to aquatic biomes pose to organisms In general water availability is of course greatly decreased in terrestrial environments as compared to aquatic environments In addition terrestrial environments also experience much greater and more rapid fluctuations in than do 39 39 aquatic 39 In fact the distribution of the majorterrestrial types is in large part influenced by temperature and water availability as you can see in the illustration here Notice on this figure of the major biomes of North America that each biome is characterized by a fairly distinct range of temperature and precipitation combinations Forthe most part the temperature and precipitation characteristics of different biomes do not overlap Now let s investigate some of the major global terrestrial biomes and learn a little about their characteristics We ll start with the most biologically diverse biome of all the tropical forest 5 Warm temperatures 9 high precipitation 391 39 very diverse organisms t Tropical forests as their name implies are almost exclusively found in the tropics that region of latitude between the Tropic of Capricorn and the Tropic of Cancer These forests are characterized by high annual rainfall up to 400 cm annually and consistently warm temperatures usually 25290 C yearround Tropical forests are further differentiated as being tropical dry or tropical rain forests In tropical rain forests rain falls yearround while in tropical dry forests there is a dry season which lasts for approximately half of the year Tropical forests hold the greatest portion of biological diversity of any biome terrestrial or aquatic This is at least in part due to the combination of high light availability high water availability and warm temperatures The combination of these factors leads to high rates of plant growth Which in turn greatly encourages the presence of other types of organisms such as bacteria fungi and animals It is also interesting to note that the soils supporting such concentration and diversity of life are actually relatively nutrientpoor The combination of warm temperatures and high moisture greatly favor rapid decomposition of organic matter And just as dead organic matter is rapidly decomposed its breakdown products are rapidly incorporated again into new organic matter to support the rapid growth of living organisms Tropical Forest Epiphytes at r 7 Tropical forests are stratified Epiphytes arrows take advantage by growing on other plants Mtp mm numa4yvv Tropical forests much like many aquatic habitats are stratified in regard to light availability and to a lesser degree temperature The light available for photosynthetic organisms greatly decreases as one moves from the dense canopy or uppermost layers of the forest foliage down to the forest floor Temperature wind and even water availability also vary from the canopy to the forest floor As a result various levels within tropical forests provide many different opportunities for diverse organisms and ecological associations Asjust one example consider the epiphytes that often cover the branches of tropical trees Epiphytes which include many species of plants in the orchid and bromeliad families among others are specialized to simply grow on other plants even though they do not gain any other direct benefit from their hosts This assisted increase in elevation allows epiphytic species to more effectively compete for sunlight In turn epiphytic species have adapted to gain their moisture by capturing rainfall or absorbing water from mist and to gain nutrients from dust leaf litter and animal activity Very low precipitation can be hot 50 C or cold 30 C While tropical forests are the wettest terrestrial biome deserts are entirely at the other end of the spectrum Typically deserts receive less than 30 centimeters ofprecipitation per year In some desert regions rain may fall only once every few years For the most part deserts are found between 20El and 40El latitude in the northern and soLthern hemisphere While light is usually abundant lack of water severely limits the ability of deserts to support life Temperatures o en also present a challenge in hot deserts temperatures o en exceed 50El C while in cold deserts temperatures may drop to 30El C or lower The extreme conditions of deserts have led to many interesting and unique adaptations in the organisms which inhabit them Most adaptations involve ways to conserve water while avoiding the intense light ofthe sun Perennial desert plants for instance are generally covered with a thick waxy cuticle and o en have very small leaves if they have leaves at all Many desert plants have also developed a modified version of photosynthesis Crassulacean acid metabolism C photosynthesis which allows them to perform photosynthesis more ef ciently while minimizing water loss There are also many adaptations in animals from physical to behavioral adaptations Some desert animals live underground to avoid intense heat some are only active at dusk or during the night while others have evolved body plans or behaviors that minimize contact with the hot ground surface during the day Many animals also have physiological adaptations to conserve water Coniferous Forests Mid to high latitude in northern hemisphere cool to cold 39 intermediate precipitation Another terrestrial biome the coniferous forest refers to a band of forested area found roughly between 500 and 700 latitude in the northern hemisphere As the name suggests coniferous forest also referred to as boreal forest or taiga is dominated by various conifer species such as spruces firs and hemlocks Coniferous forests are generally cool to cold largely due to their latitude and receive low to middlerange amounts of precipitation usually between 30 and 70 centimeters per year The organisms that inhabit coniferous forest just as with any other biome display some specialization for existing in the prevailing conditions It is likely for instance that the coneshape of coniferous trees is useful to prevent excessive accumulation of snow on a tree Many animals living in these regions have seasonally thick coats to protect them from harsh winters and some hibernate during the colder winter months Other animals such as many songbirds migrate to coniferous forests only during the milder summer months leaving before winter returns Temperate Broadleaf Forest ouvmmv gummyquot m mum Mmmmm Dominated by 39 deciduous trees four distinct seasons The last terrestrial biome that we will discuss in this lesson is the temperate broadleafforest The temperate broadleaf forests ofthe world are primarily found in the northern hemisphere between about 30El and 60El latitude although relatively smaller regions also exist in southern Australia and Z are c 39 air amounts of precipitation 70 to 200 centimeters per year spread oLt over four distinct seasons summer fall winter and spring Temperatures range from typically at or below 39eezing in the winter months to hot and humid 30El C or higher in the summer months Temperate broadleaf forests are somewhat similar to the tropical forests in that they exhibit a strati ed structure a relatively dense forest canopy covers a layer of shorter trees which in turn covers a layer of shrubs and herbaceous plants sprawling over the ground It is common though to nd relatively denser undergrowth in these forests as compared tothe tropical forests as the broadleaf species tend to losetheir leaves during the fall and winter months emosing the forest oorto relatively greater amounts of sunlight In addition the soils of temperate forests are typically much richer in nutrient content than are the soils oftropical forests As with all of the biomes we have covered the organisms that exist in the temperate broadleaf forests exhibit both physical and behavioral adaptations re ective of their environment Consider the broadleaf trees for example that lose their leaves in the fall and winter In a sense these trees are hibernating through the winter months when both temperatures and sunlight availability are low enough to effectively prohibit photosynthetic activity Animals too often hibernate or migrate for winter They also show many adaptations to emloit the different layers of the forest from the canopy to the soil v extant habitat stratified sediment and and bird species fossilized feathers 94 As you move into the following lessons and through this course keep in mind that the biome types present on Earth today have been present for millions of years although their locations and species composition has been different at different times in Earth s history In addition and perhaps more importantly the forces that affect the structure and development of biomes and the organisms that exist in them have also been present for many millions of years The biomes that exist on our planet today provide just a brief snapshot of the lengthy and complex history of our planet and the life that exists on it However even the information contained in Earth s contemporary biomes is staggering and coupled with the information contained in the geologic and fossil records it is possible to gain great insight into the history and perhaps the future of our planet Animal Behavior Orga ms Respond to Th Env ronment All forms oflife from bacteria to animals sense and respond to their environment 241 39 L The response of organisms to their environment is a crucial part of survival and as we have seen a key component of ecology For example plant roots must grow toward sources of water and nutrients Wnile plant leaves and stems must grow to effectively capture sunlight Bacteria on the other hand may increase or decrease their rates of cell division in response to fluxes of nutrients in their environment In all forms of life one finds such coordinated responses to environmental stimuli that allow organisms to more effectively interact with their surroundings In the animal kingdom such responses are often fairly complex or elaborate and are referred to by scientists as behavior Behavior can refer to many aspects of animal activity from physiological responses such as the production of hormones at a certain time of year to physical activity such as migration In this lesson you will learn about several basic types of behavior that are found in the animal kingdom and their significance to the organisms that exhibit them Innate Behavior 39 Under strong genetic control example smiling and crying in human newborns iii In general behavior can be divided into twotypes innate and learned behavior Some behaviors in the animal kingdom are specific to certain types of organisms and develop almost regardless of the environment Such behaviors are referred to as innate behaviors For example human babies are capable of both smiling and crying from the moment they are born even though they have not been taught to do so and may receive no immediate response to their behavior Cuckoos a type of North American forest birds display another wellknown example of innate behaviors in the animal kingdom In cuckoos parents often lay their eggs in the nest of other birds which in turn raise the cuckoo young as their own However as the cuckoo matures it takes on the behavioral characteristics of its biological parents rather than its surrogate parents In other words the cuckoo isjust cuckoo about being a cuckoo 39 Innate behaviors are found in many organisms in some birds migration behavior is innate Innate behaviors are fixed in the developmental programs of certain types of animals It is reasonable to assume then that such behaviors are at least in part genetically controlled As with the cuckoo it is not altogether rare to find seemingly complex behaviors hardwired into the genetic programming of species In many migratory birds the very act of migration has been shown to be under strong genetic control Studies with captive migratory birds have shown that such birds have a migratory restlessness during migration season during Which their directional movements strongly tend toward the direction of their normal migration path These young geese have imprinted on their parents These geese may have imprinted on their breeder 5w As opposed to innate behaviors the learned behaviors of animals develop largely due to environmental stimuli and are able to be modified based on an organism s experiences A common example of learned behavior is the imprinting that occurs in the young of some animals Imprinting Which is very common in bird species occurs when young of a species first recognize another organism as a parent figure In most cases the first other organism that newborn animals see is their parent From that point neWoorns quickly learn to associate their parent with food and protection In some cases however offspring happen to see other organisms before their parents and so imprint on them instead This often happens for instance When humans raise ducks or geese from eggs The first parentfigure that the newly hatched birds see and Which they associate with food and protection is their human parent Because of this chicks will follow around the person on which they imprinted and even develop some of their behaviors Imprinting is also interesting because it is a timesensitive phenomenon In other words organisms that imprint have a sensitive period during which they exhibit a strong tendency to imprint and after which they are capable of imprinting much less if at all In part because of this characteristic of imprinting it is believed that there is a least some genetic component my Learned Beha Hab39tuation 39 In habituation animals lose sensitivity to a stimulus after repeated exposure with no reward or punishment Another important type of learned behavior is called habituation In habituation organisms actually learn to decrease their response to a particular stimulus after repeated exposure to the stimulus with no consequence This is somewhat akin to the story of the boy who cried wolf In that story a ywng sheepherder cried wolf so many times when there was no wolf that people learned to ignore his warning cries Even though habituation in this story led to serious consequences it is thwghtthat habituation is otten beneficial to animals as it allows them to focus more strongly on stimuli that are associated with actual positive or negative effects blue jay Cyanococitm crismh monarch butterfly Danaus plexippus Bluejays can learn to associate orange butter ies with a bad taste a ry butter y Li enin39s archippgs i39 As opposed to habituation another type of learning called associative learning involves animals recognizing the relationship between certain stimuli and their positive or negative effects For example a bird that normally preys upon butterflies may capture and attempt to eat a brightly colored butterfly such as a monarch that is completely unpalatable If this experience is strong enough or is repeated enough times the bird may learn to associate the bright colors of the monarch butterfly with its bad taste and so will not prey on those butterflies anymore Interestingly enough this phenomenon may also bring a benefit to other butterflies that resemble the bad tasting monarch as birds will also bypass them as prey items due to their physical appearance This and other types of mimicry will be covered in a future lesson Learned Behavior Cognitive Learning Involves synthesizing information to solve problems 39 more prevalent in some groups primates dolphins g Perhaps the most complex type of learning is called cognitive learning Cognitive learning involves the ability of animals to not only receive and store information but to also combine different sources of information and solve problems Cognitive learning is also often associated with the presence of consciousness or self awareness As one example consider a group of chimpanzees placed in a room In the room there are sticks on thefloor and food that is too high up to be reached by the chimps alone In this scenario the chimps eventually utilize the sticks to reach the food source It isn t that sticks are directly associated with food in the chimpanzees experience but they are representative of a tool that in this case can be used to solve the problem of how to get to the food It is doubtful Wnether cognitive learning occurs in all or even most animals Cognitive learning seems to be more prevalent in certain groups of animals such as the primates and dolphins Pack animals maintain social hierarchies through agonistic behaviors In all animals part or all of the life ofthe animal is spent in association with others of the same species During these times various social behaviors occur in response to association with others within the community as well the most effective competitors or the most vigorous individuals regularly gain the best access to resources Agonistic behavior then is o en viewed as an example of natural selection sexual selection or both Dominance hierarchies and agonistic behavior are perhaps most clearly observed in carnivores that maintain packs such as wolves and lions In these cases there generally is a dominant male and female which tend to obtain relatively better access to food and mating resources However agonistic behavior is also common in the territorial behavior of various animals While the details may vary such as how large territories are whether the male or female keeps the territory and how many s exist in a territory territorial behavior is generally based on displays of physical prowess or overall health Some types of organisms such as many cats and dogs even go so far asto physically mark their territory such as by spraying urine on objects at the edge oftheir territory The main bene t to keeping a territory is decreased competition for the resources that exist in it OC 9 S ial Behavior39 Matin U1 East Asian redcrowned cranes Grusjaponicus Mating behaviors can be very simple or very elaborate While agonistic competition often plays a significant role in mating not all mating behavior is agonistic In many animals various types of courtship behaviors have evolved to entice members of the opposite sex into mating In some cases such as with various invertebrates mating rituals may simply involve the vibration or wiggling of a body part In other cases such as in various species of cranes mating rituals may involve fairly complex dancing and vocalization We will not make comment here about human mating rituals they are way too complex Behavior has played an integral role in the evolution of animals As you have seen behavior and social interaction among animals can involve a wide variety of stimuli and responses ranging from visual olfactory and auditory to tactile cues and reactions In some cases behavior is as simple as recognition of a stimulus In other cases behavior can involve complex movements or sounds Behavior be it simple or complex is an integral part of how animals interact with their environment and has played a major role in the history of life on our planet