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1/12/17 Through natural selection, animals have modified both their behavioral and physical characteristics to better equip themselves to meet the demands of their environment. An organisms ability to adapt is key to its survival and may give arise to new species. Through continual adaptations you may get the formation of new species. This process of species formation is called speciation. Species are defined as members of populations that actually or potentially interbreed in nature. San Francisco Zoo 1 1/12/17 Species may have adapted to reduce competition for food. Koalas occupy a unique niche in that they consume eucalyptus leaves which are poisonous to most other animals. Giraffes eat the leaves of the acacia tree that other animals can not reach. In turn, the acacia avoids being eaten by growing up tall first and then spreading out with its leaves like an umbrella. The acacia will also exudes a bitter chemical through its leaves as it it eaten. In response, the giraffe moves on. The tree is not overgrazed and is available as a food source later. Flamingo’s beaks are adapted for filter feeding. The sharply downward bent bill is held upside down in the water and swept back and forth. The fleshy tongue pumps water through comb-like filtering structures lining the top half of their bill, filtering out the minute organisms. The form of the beak allows them to feed without getting the feathers wet. An adaptation may be a defense response to protect themselves and their young from predators, pests and weather. This would include things as protective coloration or eyes on the side of the head for prey animals. Having eyes on the side of their head allow these animals to see everywhere except directly behind them. With ducks and zebras, you may have individuals facing in both directions to spot predators from all directions. Ducks can have one side of their brain sleep while the other side remains awake watching for predators. Animals must be able to move throughout their habitat and have locomotion adaptations. Feet have morphed into fins for swimming or arms that have evolved into wings for flying, legs have been made longer for jumping or running faster. Adaptations may relate to reproduction or the perpetuation of species. Individuals must recognize their own species, attract a mate and raise young. Cats (excluding lions) are solitary that occupy different but overlapping territories. Both sexes scent mark their territories. The male constantly checks these scent messages as he roams his territory. When he encounters an estrous female, he will track her down. A non-estrous female may shun him. Marsupials, like this koala, lack a true placenta and are born in a minimally developed state. Newborns climb to the pouch and latch themselves onto a teat and remain while they continue to develop and are ready to come out of the pouch. In the kangaroo, the mother mates shortly after giving birth and the fertilized embryo develops into a blastocyst of 85 100 cells, and then becomes dormant. While the female is nursing an offspring (joey) in the pouch, the blastocyst remains dormant. When the joey stops nursing due to weaning or death the blastocyst resumes development. A female may have three offspring simultaneously in different stages of development; the blastocyst, the joey in the pouch and a partially weaned offspring (referred to as young-at-foot). The female produces milk for the joey and a different, richer one for the young at foot. San Francisco Zoo 2 1/12/17 An adaptation may be an external physical feature such as coloration. Color or patterns can be used as camouflage or for identification. The lighter coloring of the kangaroo may keep it cooler in the heat of day in Australia. An adaptation of size or shape enables it to reach food such as the long neck of the giraffe allows it to eat leaves on the taller trees. A larger body size can keep you warmer in a cool environment. Otters and penguins have very streamlined bodies for their water environments. The male of a species might be larger than the female and the larger size may help him compete for the right to mate with a certain female. When you are at the zoo look at the various species and observe their features such as eyes, hands, tongues, ears or toes. These may serve a special purpose. The feature might give them an advantage when they move or when they are hunting for prey. It might help them locate food or sense predators or a mate. Be observant out there. The adaptation might not be something you can see but is beneficial to it’s survival. It may be an internal physiological adaptation. It might be a four-chambered stomach that the ruminants have adapted to ease digestion from their herbivorous diet. Giraffes, antelopes and cows have this adaptation. Birds have adapted a light skeleton for flying, Scimitar-horned Oryx are able tolerate higher body temps and have specialized kidneys to reduce water loss. Lastly adaptations can be behavioral. You might see social behaviors of animals living in groups or alone. You might see animals defending their territory or in the gorilla community where the male is dominant in a social grouping of females and young. You might see animals resting during the day because they are nocturnal and do their feeding at night. The zebras and rhinos may roll in the mud to protect their skin from sun and insects. These are only a few of the many adaptations that animals have. The more you learn about an animal’s adaptations the more amazing they will become to you and the more you will want to learn about an animal or plant. San Francisco Zoo 3 1/12/17 Camouflage is an excellent example of a external physical characteristic. Coloring helps an animal blend into its environment and avoid detection. A dry, savanna animal will be tan or brown, a wet, rainforest animal will be glossy green, and so forth. Coloring may also have a physiological benefit; lighter colors reflect more of the sun’s radiation than a darker one and thus helps them to remain cool. Other animals use textures and patterns to help them to blend in; the patterns may resemble shadows and windblown vegetation. Other patterns may appear confusing for predators and make it hard to find an individual in a group. Other animals have countershading camouflage where they have dark backs and light underneath. Many birds and ocean fish have this countershading. The magellanic penguins at the zoo are no exception. From above the penguin look like the ocean floor and from below, like the sun or bright water surface. Another example of countershading is seen in koalas, who spend all their time sitting in a tree and have whitish fur below and darker fur along their backs and head. Coloring can be a warning signal to predators to stay away (aposematism). In the case of the poison dart frog, their coloring warns potential predators that they are poisonous to eat. San Francisco Zoo 4 1/12/17 After each animal is listed an adaptation. Select if it is a physical or behavioral adaptation. A giraffe’s 18 inch prehensile tongue is an example of an external physical adaptation for grabbing leaves from tall trees. A kangaroo licking its palms is a behavioral adaptation for staying cool. Rhinos rolling in mud to is another behavioral adaptation to protect their skin from sun and insects. Oryx’s ability to increase their body temperatures and decrease their metabolic rate is an internal physiological adaptation. This ability allows them to suppress sweating and minimize their panting, thus conserving water. Oryx are able to raise their body temps to 116 degrees Fahrenheit without sweating. Producing a shrill alarm cry by a meerkat is a behavioral adaptation that warns the others to seek the burrows for safety. Another behavioral adaptation is they take turns as sentry while the others feed. The bright colors of the peacock versus the dull colors of the peahen is a external physical feature but the displaying of the colorful tail feathers of the male is a behavioral adaptation to attract a female. San Francisco Zoo 5 1/12/17 In these pictures you can see the three species of Zebra: the plains zebra, the Grévy's zebra and the mountain zebra. What is the mechanism where different species arise? Speciation happens when a subset gets isolated from the rest of the population and don’t interbreed any more. One population may be developing traits in response to environmental characteristics that are present only for their population, passing on features distinctly different than those of the first population. This reaches a point where the two populations are different enough that they can no longer reproduce with each other, and a new species evolves. This was the case of the three species of zebra who occupy locations in Africa. This is a slow process which usually involves development of subspecies first. Subspecies may never progress to full species in some cases. If one looks at the geographic distribution of related species, one can see evidence of speciation. Islands and continents separated over time show distinct differences within and among species. Madagascar is a prime example of having a large number of endemic species that can be found no where else in the world. The most likely explanation for the existence of Madagascar’s mostly unique biotic environment is that the life forms have been evolving in isolation from the rest of the world for millions of years. San Francisco Zoo 6 1/12/17 Adaptive Radiation is the evolution from one kind of organism to several divergent forms, each specialized to fit a distinct and diverse way of life. Examples came be seen in Darwin’s finches or in these African cichlids. Adaptive radiations often occur as a result of an organism arising in an environment with unoccupied niches, such as a newly formed lake or isolated island chain. The colonizing population may diversify rapidly to take advantage of all possible niches. Another excellent example of adaptive radiation is lemurs in Madagascar. In the absence of competition from monkeys and apes, many types of lemurs developed with over 40 species still in existence today despite loss of number due to human hunting, habitat loss, etc. Adaptive radiations commonly follow mass extinctions. Today there is good evidence that a major meteorite impact occurred at the end of the Cretaceous Period, leading to the extinction of non-avian dinosaurs resulting in the rise of mammals. Before this time, mammals were barely existing in the shadow if the dinosaurs for millions of years. When the dinosaurs went extinct, these mammals blossomed into the wide diversity of species we see today. Which was good for us as humans. San Francisco Zoo 7 1/12/17 Lets discuss some mechanisms that may prevent breeding between two species. Geographic isolation happens when species occur in different areas, and are often separated by barriers. Madagascar's lemurs were isolated from evolutionary changes of the rest of the world and radiated into the large island's many niches without much competition or predation. Ecological isolation occurs when species occupy different habitats. They do not encounter individuals of other species with different ecological preferences. The lion and tiger overlapped in India until 150 years ago, but the lion lived in open grassland and the tiger in forest. Consequently, the two species did not hybridize in nature. Temporal isolation occurs when species breed at different times. This may be different times of the day or different seasons. In North America, five frog species of the genus Rana differ in the time of their peak breeding activity. Behavioral isolation is when species engage in distinct courtship and mating rituals. Individuals of different species may meet, but one does not recognize any sexual cues that may be given. Mechanical isolation occurs when interbreeding is prevented by structural or molecular blockage of the formation of the zygote. Mechanisms include the inability of the sperm to bind to the egg in animals, or the female reproductive organ of a plant preventing the wrong pollinator from landing. San Francisco Zoo 8 1/12/17 Convergent evolution describes the independent evolution of similar features in unrelated species; through natural similar traits or adaptations have resulted from species adapting to similar environments or ecological niches. In this example here, sharks and dolphins have independently developed streamlined bodies allowing for rapid movement through their water environment. Another example would be a bat’s wing versus a bird wing; both are different approaches to flight. Within our own Children’s Zoo the meerkats and prairie dogs both have communal underground lifestyle but meerkats are carnivorous, from Africa and are in the Family Carnivora, whereas the prairie dogs are herbivorous, from North America and are in the Family Rodentia. When you are at the Magellenic Penguin exhibit, also look at the North American River Otters. Here are two animals with very streamlined bodies for their watery environments but the penguin is a bird covered with feathers and the otter is a mammal covered by dense fur. San Francisco Zoo 9 1/12/17 Coevolution is the evolutionary change of one species triggered by the interaction with another species. How can the evolution of one species affect the evolution of another? Every form of life on Earth interacts over time with other organisms, as well as with its physical environment. Predator/prey relationships are a classic example of how two species influence each other. Predators and prey are involved in an endless competitive tussle, a “cat-and-mouse” game, which has giving rise to physical and behavioral adaptations, resulting in coevolution of both the predator and the prey. Predators are under strong selection to evolve more efficient hunting strategies. In response, the prey is under strong natural selection to evolve better predator evasion techniques. Predators and prey are constantly adapting, evolving, and proliferating not merely to gain reproductive advantage, but also simply to survive while pitted against ever-evolving opposing organisms in an ever-changing environment. In general, when we look for examples of adaptation that have evolved between predators and prey, we tend to find there's a wider or more diverse range of prey adaptations to escape capture than there are predator adaptations to enhance capture. If a predator doesn’t adapt to a changing prey, they just lose a meal, whereas, if the prey doesn’t adapt they die. Predator’s typically eat a wide range of prey items; evolving a specific response that improves the capture over one prey type, might compromise its ability to capture another prey type. Prey typically have shorter generation times allowing them to adapt more quickly to better hunting strategies of the predators. Prey defense mechanisms might include sheltering in safe havens (i.e. burrows), better camouflage, prevent recognition through mimicry, cryptic and warning coloration, early detection of predator, or active defense (i.e spines, toxins). A predators counter adaptations might involve improved prey detection, learning (avoid being tricked), secretive approach or subduing skills (ie. Meerkat preying on a scorpion) or immunity to toxin. Over evolutionary time, when a predator and prey are constantly adapting and improving their strategy, the net result might not be an improved success for either predator or prey. This is due to the constant shifting nature of their relationship. One such predator-prey relationship exists between between wolves and caribou. Wolves hunt caribou, chasing them down to capture them. The slower caribou are more likely to be preyed upon, leaving the faster individuals to reproduce. The resulting faster offspring will be even more difficult for the wolves to catch, and only the fastest wolves (or perhaps the wolves who are genetically capable of devising strategies to hunt very fast prey) will get enough food to survive. Can you think of another example of relationship among our zoo animals? Perhaps an animal from Australia that consumes only eucalyptus. (Answer: Koala eat only eucalyptus that are toxic to most animals) As we will see later in our plants and animal module, co-evolution is especially seen among plants and their pollinators. A number of species of flowering plants have coevolved with specific pollinators (i.e. insects, bats, birds). The pollinator gets a reward such as nectar for pollinating the plant. San Francisco Zoo 10 1/12/17 The English Peppered Moth is typically a mottled white with black making them well-camouflaged against lichens on tree trunks. Occasionally a very few moths have a genetic mutation which causes them to be all black. Black moths resting on light-colored, speckled lichens are not very well camouflaged, and so are easy prey for any moth-eating birds. With the Industrial Revolution, many factories and homes started burning coal. This created a lot of black soot and pollution which killed the lichens and settled out everywhere, turning the city tree trunks black. With the settling of the soot, the population of peppered moths was found to contain more black moths. This is an example of: A. Extinction B. Adaptive Radiation C. Natural Selection D. Convergent Evolution The correct answer if C. Natural Selection The black soot on the trees enabled the occasional black moths living in the cities to be well-camouflaged so they could live long enough to reproduce, while the normal speckled moths were now more visible and they were gobbled up. The English Peppered Moth adapted to its new environment. San Francisco Zoo 11 1/12/17 San Francisco Zoo 12 1/12/17 Definitions: Species: an individual belonging to a group of organisms having common characteristics and are capable of mating with one another to produce fertile offspring. Speciation: the process of species formation. The isolation of populations results in development of different gene pools and resultant different traits. Islands and continents separated over time show distinct differences within and among species as a result. Shift of continents over time results in distinctly different types of animals/plants on various continents and islands. Reasons two species will not breed can be geographical, ecological, temporal, behavioral or mechanical. Adaptive radiation: process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches Convergent evolution: unrelated species can develop similar traits as the process of natural selection results in the same solution to a similar problem. Coevolution: The process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another; two (or more) species reciprocally affect each other's evolution; the evolutionary change of one species triggered by interaction with another species. San Francisco Zoo 13