1.3 Variation within Species PDF

1.3 Variation within Species Healthy Ecosystems ▪ Healthy ecosystems have great genetic diversity among the species which inhabit them. ▪ “between-species diversity”: differences between organisms of different species ▪ They also have great variation within a population of a singl...

1.3 Variation within Species Healthy Ecosystems ▪ Healthy ecosystems have great genetic diversity among the species which inhabit them. ▪ “between-species diversity”: differences between organisms of different species ▪ They also have great variation within a population of a single species. ▪ “within-species diversity”: differences between organisms within the same species ▪ Variation of a single species within a population is called variability.  Variations within a Species ▪ Sexual dimorphism: when the males and females of a species are structurally different ▪ Ex. peacock where the male’s bright colors help attract a mate and the female’s bland camouflage helps hide her while she sits motionless on the egg ▪ Polymorphism: where there are several distinct forms within the same species; different roles ▪ Ex. insects, beads, ants, termites, where each distinct form has adaptations for its specific function (role) such as reproduction, self-defence, obtaining food etc. ▪ Metamorphism: which implies a dramatic change in an organism’s structure or appearance at some stage during its life cycle ▪ Ex. tadpole to frog, caterpillar to butterfly, maggot to fly etc.  Variations within a Species ▪ Developmental changes in the normal life cycle of an individual in a species ▪ Differences between babies, adolescents, adults, senior citizens such as differences in size, strength, intelligence, and appearance (wrinkles, grey hair etc) etc. ▪ ‘Normal’ variations in external appearance ▪ Skin, fur, eye color, or the presence of stripes/spots etc. ▪ Adaptations that change with the seasons ▪ Deciduous trees (grow leaves in summer and shed in winter), fur thickness (thicker/warmer in winter, thinner/cooler in summer), color (white rabbits in winter and brown in summer for camouflage), sun tan (better protection from UV light in summer but lighter skin for better absorption of light in water to better make vitamin D) etc. ▪ Birth anomalies/mutations ▪ Freckles, birthmarks, Siamese twins, cerebral palsy, albinos, etc. ▪ Healthy vs. unhealthy living standards ▪ Disease and malnutrition may result in short-term or long-term effects ▪ Different life/behaviour/cultural “choices” ▪ SUMO wrestler vs. bodybuilder vs. marathon runner, or desert tribe vs. Inuit, or body manipulations such as rings to stretch necks vs. tattoos vs. scaring etc. ▪ ‘Normal’ genetic variability ▪ Different personalities, immune systems (sick easily vs. not), athletic bodies, or math skills (strong vs. weak) etc. Variability and Survival ▪ Variability is important if the environment in which the species lives changes suddenly or drastically. ▪ When a species has a great deal of variation, then, some of the individuals within that species will likely survive when there is change (different environments or environmental change) Variability and Survival ▪ Example ▪ A half of a colony of roughly 60 000 cliff swallows in Nebraska died during a six day cold snap in May 1996 ▪ The ones that survived were larger (ie. stored more fat) and were more symmetrical (ie. could forage for food with less energy loss). ▪ Swallow video Examples of variability include: ▪ Red fox (color of coat -red vs. black) ▪ Antibiotic resistance (bacteria) ▪ Banded snail (color of shell-yellow to pinkish brown to brown) Low variability -Pando Activity  Adaptations ▪ The adaptations of an organism/species are all the traits that an organism/species possesses that allows it to survive and reproduce in a particular environment. ▪ Adaptations are closely linked with the ecological niche of the species ▪ Structural adaptations vs. behavioural adaptations ▪ Structural adaptations ▪ Physical features/traits the organism possesses ▪ Internal structures (inside organism) Ex. gills, lungs, big heart ▪ External structures (outside organisms) Ex. furs, fins, feathers, claws, fangs, big eyes, sensitive ears ▪ Behavioural adaptations ▪ Behavioural patterns that organisms do to survive and reproduce ▪ Ex. migration, courtship dances, building nests, nocturnal  4 Main Categories of Adaptations 1. Help protect an organism from predators (avoid being eaten) ▪ runaway (fast, fly, jump, swim, run) ▪ hide (camouflage, stillness) ▪ defend (teeth, claws, strength, herds, sting, poison) ▪ avoid (great senses, nocturnal, live in hard-to-get-to places (cliff face, high in trees etc.) ▪ intimidation (call, cry, scary appearance) Ex. cats puff up & hiss ▪ armour (tough skin, shell, exoskeleton, fur, blubber, quills, spikes) ▪ unappealing (bad taste, smell, poisonous if eaten) Ex. puffer fish 2. Help protect an organism from climate/weather (survive the elements) ▪ insulation (increased fur, blubber thickness) ▪ blood circulation (reroute blood from extremities to more essential core organs) ▪ anti-desiccation (decrease water loss) Ex. cacti store water & have thick wax covered thorns ▪ sweating (to cool off) ▪ behavioural (hibernate, migrate)  4 Main Categories of Adaptations 3. Help an organism obtain food & water (obtain food and drink) ▪ predation (ability to kill via strong jaws, paws) ▪ behavioural (pack hunting, sneaking & pounding, tracking to find prey, storing food for winter) 4. Help an organism reproduce & pass on useful adaptations (reproduce) ▪ type of reproduction (sexual vs. asexual) ▪ time of mating season ▪ extra sexual competitions/contests to establish hierarchy ▪ life cycle Ex. caterpillar/butterfly or a frog ▪ sexual dimorphisms, etc. ▪ parental care *Some adaptations do not fit into these 4 categories and a single adaptation may fit into all 4. Variations in Adaptations ▪Within a species, there are variations in adaptations. Organisms are considered the same species if they reproduce in nature and their offspring are able to reproduce. ▪Variation in adaptations and variation between organisms within the same species or between organisms of different species influence which organism will survive and reproduce. The variation may give one organism an advantage, making them more successful. ▪Over time organisms/species evolve to retain the adaptations that made it most likely for them to survive and reproduce. The traits that made them more “fit” gave them the “tools” to survive and reproduce at a greater rate. ▪ This is the basis of the foundations of Charles Darwin's Theory of Evolution by Natural Selection. ▪ The most important struggle in nature is not between predator and prey but between members of the same species, competing for limited resources. *Note: The less successful species will need to change its ecological niche (Ex. switch to a different food/habitat) or go extinct. If a species is forced to change its ecological niche, then it often begins to evolve a new set of adaptations to better take advantage of its new lifestyle. Darwin’s Finches Ex. Microevolution by Natural Selection Environmental pressure-> food source ○ Select for trait ○ Select against trait The food source that was available determined which species of finch could survive and reproduce Ex. insect eaters -> short grasping break, seed eaters-> short strong beak to break seeds Peppered Moth Ex. Microevolution by Natural Selection Pre Industrial revolution ▪ Poplar trees with white bark ▪ Light colored moths survived more than black moths ▪ Light colored population increased (were the majority in 1848) Post Industrial revolution ▪ Poplar trees covered in soot from air pollution ▪ Black moths survived more than light colored moths ▪ Black moth population increased (became the majority in 1898) Why? Result of change in the environment that better camouflaged the moth from their predators (ex. birds) and led to their survival and reproduction. It was the moths with the advantageous or favoured trait that survived. This changed the population over time. *In this example no NEW mutation was necessary as the adaptation that allowed both organisms to continue to thrive was already present in the normal, everyday variation/diversity of the population.  Pesticide Resistance Ex. Microevolution by Natural Selection ▪ San Jose scales are insects that eat apple orchards. ▪ Some pesticides are sprayed on the insects in apple orchards and kills most of the insects, yet some (with some adaptation that makes them immune to the pesticide) survive and then these special ‘pesticide resistant’ ones (ones with the advantageous or favoured trait) survive and reproduce more often (while the ‘normal’ ones keep getting killed by the pesticide) and soon the entire population is ‘pesticide-proof’ and thus the pesticide is no longer effective. The insects have changed/evolved! ▪ *In this example no NEW mutation was necessary as the adaptation that allowed both organisms to continue to thrive was already present in the normal, everyday variation/diversity of the population. Antibiotic Resistance Ex. Microevolution by Natural Selection ▪ Antibiotics, like penicillin, would work forever but the bacteria evolved resistance, some bacteria were antibiotic resistant (Superbugs) ▪ The antibiotic resistant bacteria survived better and spread their resistance to successive generations through reproduction, and continue to do so ▪ Old antibiotics don’t work anymore, and new ones must constantly be developed. ▪ Antibiotics should be used sparingly. Vaccines ▪ May need to develop new vaccines due to strains evolving resistance. ▪ Ex. new vaccines for the flu ▪ Ex. may need new COVID 19 vaccines  Natural Selection ▪ Thinking back to the swallow example, due to the fact that swallows that survived the cold snap were mainly large and symmetrical, most of their offspring were also large and symmetrical. This is known as natural selection. ▪ Natural selection happens when factors in the environment determine or ‘select’ which individuals within a species will be able to survive. If they are able to live long enough to reproduce, then those individuals with ‘survival adaptations’ will have offspring with similar survival characteristics. ▪ This occurs when the environment favours certain variations/characteristics over others allowing those individuals to survive and reproduce. Video  Theory of Evolution by Natural Selection The theory of evolution by natural selection can be summed up in five statements: 1. OVERPRODUCTION: All organisms produce more offspring than can possibly survive, reproduce, and live to maturity. ▪ Some offspring must die, because simply there isn’t enough food/space/resources for all of them 2. COMPETITION (struggle for existence): Due to overproduction, organisms of the same species and organisms of different species, must compete for limited resources (food, water, lodging etc.) and there isn’t enough for all organisms so some must die. 3. VARIATION/DIVERSITY: There is incredible variation (difference/uniqueness) within each species. Differences among traits occur among members of the same species such that no two individuals are exactly the same. 4. NATURAL SELECTION (survival of the fittest): Some of these variations (that give them an advantage in this environment) increase the chances of an organism surviving to reproduce in this environment. These organisms are better adapted to their environment. They are better able to compete, survive, and reproduce, while others die off without leaving offspring. Those individuals/species with the best adaptations for that time and place will live and reproduce more successfully and thus pass on their successful adaptations down to the next generation more often. Those species/individuals with unselected traits will die more easily and not pass down their (less successful traits) as often, and thus these bad traits die off. The population has evolved. 5. SPECIATION (origin of new species): Over time (100s/1000s/millions of years) and over successive generations, variations that are passed on lead to changes in the genetic characteristics of a species. A new species may slowly emerge/evolve by the accumulation of inherited successful variations, as species reproduce over many generations. When/if a new organism is produced that is significantly different from the original, then it is said to be a new species, and thus a new species has evolved from a previous one. *Note: Older species may lead to a new species over time or they may become extinct instead or they may just stay the same if their adaptations are still the best for their niche.  Theory of Evolution by Natural Selection All species and organisms arise and develop through the small natural selection of traits ▪ (a.k.a. variations/adaptations) that all it to compete, survive, and reproduce at a greater rate than other organisms. ▪ The adaptations are heritable, which means that they are passed on from one generation to the next. Our traits are passed down from parent to offspring by means of passing on our DNA through reproduction. ▪ If the adaptation makes it more likely that an organism will survive and reproduce, then that adaptation will be passed on to the offspring, therefore surviving over generations and generations of organisms. This takes time. ▪ The traits are “selected for” because of the environmental conditions (ex. climate, competition etc) in the ecosystem dictate which traits are “best” or “favoured.” ▪ Only the traits that are best suited to the ecosystem will contribute to the survival of a species. ▪ The term evolution by natural selection does not refer to individuals changing, only to changes in the frequency of adaptive characteristics in the population as a whole. *Fitness= the ability to survive and reproduce *Survival of the fittest= the organisms with the greatest fitness will survive and reproduce at a greater rate Ex. seal blubber helps seal survive cold water and climate therefore, it remains a trait and makes the organism more fit How do organisms get traits that make them more fit? DNA *DNA codes for all traits in all living things; DNA is organized into genes, genes code for traits that can give organisms an advantage over others to survive and reproduce (two major goals of all organism) Evolution ▪ The cumulative inherited change in organisms over time ▪ Leads to speciation, the formation of new species ▪ The process through which similar species become more and more different and eventually evolve into separate species. ▪ At a certain point, the species are so different that they cannot interbred, therefore, two species now exist where formerly there was just one. ▪ The primary mechanism of evolution is natural selection Evolution ▪ Microevolution: changes in gene/allele frequencies (thus genetic characteristics) over time, in a given population of species ▪ It is within the same species. ▪ Ex. moths are still moths in peppered moth earlier example ▪ Ex. insects are still insects in San Jose scales earlier example ▪ Evolution doesn’t necessarily improve a species (can also make it worse or inferior) ▪ Ex. If pollution was prevented or cleaned up, the moths would probably revert back to being light colored. ▪ Ex. Pesticide resistance may be a disadvantage in a pesticide-free environment because it could slow the insect down or require more energy to build say an extra thick exoskeleton to protect it from the pesticide. ▪ Evolution doesn’t necessarily imply progress (myth). ▪ Ex. mother evolved to produce big headed babies yet many of both die during birth ▪ Ex. fish cut-off in caves evolve to have no eyesight ▪ Ex. bacteria evolved a loss of cell wall when exposed to penicillin which attacks their cell wall Human Evolution ▪ The mechanism for human evolution will be much the same as the mechanism seen in the earlier examples ▪ There will be some change in the environment of the species which will give any organism with one set of adaptations an advantage over any organism that doesn’t possess those key advantages ▪ In the case of humans, a change in culture can be just as influential on such evolution as a change in climate ▪ Ex. our culture has changed our environment such that we spend much more time sitting in artificial environments (watching TV, using a computer, sitting at a desk) and so should expect such a change in behaviour/environment to lead to a corresponding change in our biology, through evolution Evidence of Evolution Suggests common ancestor 1. Fossils 2. Biogeography 3. Comparative anatomy 4. Embryology 5. Biochemistry *Note: We will discuss artificial selection later in this course. It can also provide a form of evidence of evolution.  Evidence of Evolution Suggests common ancestor 1. Fossils ▪ fossils sometimes form when the bodies of organisms become trapped in sediments and leave traces that can be found many years later, and provide direct and physical evidence of past life ▪ paleontology is the study of fossils and what they imply about the past ▪ discovered ~250 000 fossils, only a fraction of the species that have lived on Earth (most of us won’t leave a fossil) ▪ shows a progression from simple to complex organisms and formation of new species over millions and millions of years ▪ Key finding #1: different species have lived on Earth at various times in the past ▪ Very few of today’s species were alive 1 million years ago, and almost all species that have ever existed are now extinct ▪ Extinct organisms are different from organisms living today (because of evolution) ▪ Key finding #2: the complexity of life generally increased over time ▪ Older layers contain ‘simpler’ organisms and more recent layers contain more complicated ‘descendants’ ▪ Ex. prokaryotes (no nucleus) emerged ~3.7 billion years ago, which predates eukaryotes (nucleus) ~0.7 billion years ago  Evidence of Evolution Suggests common ancestor 1. Fossils ▪ Key finding #3: living species and their most closely matched fossils are typically located in the same geographical region ▪ Ex. all fossils of ‘ancient’ sloths are found in Central & South America, the only region where we find ‘modern’ sloths ▪ Key finding #4: more recent fossils show more similarities to current species than older fossils ▪ This is because there has been less time to evolve more differences ▪ Key finding #5: the existence of ‘missing links’ ▪ If evolution is occurring then we should see the existence of intermediate/in between species, such as so called ‘missing links’ ▪ Although the fossil record is incomplete (many simply inaccessible, or never fossilised in the first place), many such ‘missing links’ have been found ▪ Ex. “stem-reptiles” appear to be in between amphibians and reptiles Evidence of Evolution Suggests common ancestor 2. Biogeography ▪ variations and distribution of life on Earth ▪ illustrates how different environmental conditions dictated which organisms can survive and reproduce ▪ Ex. Galapagos islands were home to 13 similar species of finches which most closely resembled bird species from the South American coast (where Galapagos islands drifted away tectonically). Darwin speculated that these birds came from the coast and then developed specific adaptations that best fit the circumstances of each particular island, such as slightly different beaks for eating insects, seeds, or fruit, depending on the food source on a given island Evidence of Evolution Suggests common ancestor 3. Comparative anatomy ▪ organisms of different species share common anatomy they should have evolved from a common ancestor ▪ Ex. similarities in bone structure of front limbs in vertebrate species ▪ structures should show modifications in later organisms to reflect new adaptations that have occurred through time within that lineage ▪ Ex. bird, whale, horse, and human limbs show similar bone structures modified to fit different functions/contexts ▪ vestigial organs are reduced, rudimentary structures that serve no useful functions, but often are functionless remnants of organs that were once more prominent in ancestors. This suggests evolution from a common ancestor. ▪ Ex. whales and snakes have vestigial hip and leg bones, suggesting they have evolved from ancestors with 4 limbs Evidence of Evolution Suggests common ancestor 4. Embryology ▪ If early development (embryology) is similar it suggests a common ancestor. ▪ Embryology is fascinating because just as evolution proposes that species slowly made the step transition from a single celled organism to a larger animal, so too each individual organism makes the slow, step by step transition from a single-celled zygote to its final often multi-celled adult form, such as a human. ▪ Ex. during early development all vertebrate develop gill slits and a tail, and pass through stages when they resemble larval fishes ▪ The embryonic tail serves no function and later forms a rudimentary tailbone, while the gill slits become modified to form various structures, including the bones of the middle ear Evidence of Evolution Suggests common ancestor 5. Biochemistry ▪ If organisms descended from a common ancestor then they should be similar at the molecular level and there is a remarkable amount of uniformity among them ▪ All life (cell) is made of the same 4 basic biological/organic molecules (proteins, lipids, carbohydrates, nucleic acids) ▪ In all organisms, chemical reactions are controlled by proteins known as enzymes ▪ All cells obtain energy by breaking down compounds, like glucose, through the process of glycolysis ▪ All cells contain DNA, a molecule that carries the coded genetic information controlling the building of proteins and the development and metabolism of the cell. This genetic code (DNA) is virtually universal, like when the genes of humans are incorporated successfully into bacteria, or other animal genes into other transgenic animals Assignment -Read textbook pages: -Focus: pages NONE -Science in Action: pages 20-24 -1.3 Assignment Assignment 1. What is variability? 2. In your own words, define natural selection. 3. Describe several examples of changes in the environment that might select some individuals in a species for survival over other individuals. Explain your answers. 4. Describe an example where variability within a species has helped a species survive an environmental change. 5. Suppose a population of sparrows migrating south for the winter is blown off course by a storm and the sparrows become isolated on an island. The only food source available on the island is a plant that produces large seeds. Predict which birds in the population, those with large beaks or those with small beaks, will survive to continue their migration or to populate the island. Explain your answer. 6. Write a definition of biological diversity that includes a description of its three main components. 7. Define the terms niche and symbiosis. Explain how these terms are related. 8. How does variability within a species affect its survival? 9. Using examples, explain ways in which different species living within an ecosystem depend on one another. 10. Restate the meaning of interspecies competition in your own words. Use an example to illustrate. 11. How does variation within a species contribute to the health of the species? Of an ecosystem?