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Science 10 Q3 lesson 4 evolution and biodiversity origins niches and adaptation.pdf
- 1. SZL 121: FANDAMENTALS OF ECOLOGY Lecture 4: Evolution and Biodiversity: Origins, Niches, and Adaptation Prof. Dr William A. Shivoga (Professorof Aquatic Ecology) Masinde Muliro University of Science and Technology Department of Biological Sciences E-mail: [email protected] [email protected] Tel. 0721 264334
- 2. Core Case Study: Why Are Amphibians Vanishing? (1) • Habitat loss and fragmentation • Prolonged drought • Increased ultraviolet radiation • Parasites • Viral and fungal disease
- 3. Core Case Study: Why Are Amphibians Vanishing? (2) • Pollution • Climate change • Overhunting • Nonnative predators and competitors • 33% of all amphibian species face extinction
- 4. What is Biodiversity and Why is it Important? • The term biodiversity (from “biological diversity”) refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life • The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.
- 5. Biodiversity (1) • Species diversity • Species – a set of individuals that can mate and produce fertile offspring • 8-100 million species total; likely 10-14 million • 2 million species identified • ~50% in endangered tropical rain forests e.g. Kakamega Tropical Rain Forest
- 6. Biodiversity (2) • Genetic diversity • Ecosystem diversity –Biomes • Distinct climate • Certain species, especially vegetation • Functional diversity
- 7. Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities and ecosystems. Genetic Diversity The variety of genetic material within a species or a population. Species Diversity The number and abundance of species present in different communities Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.
- 8. Genetic Diversity of Molluscs
- 9. Coastal mountain ranges Deciduous forest Prairie grassland Coniferous forest Desert Coniferous forest Coastal chaparral and scrub Appalachian Mountains Mississippi River Valley Great Plains Rocky Mountains Great American Desert Sierra Nevada Fig. 4-4, p. 63 San Francisco Las Vegas Denver St. Louis Baltimore Average annual precipitation 100-125 cm (40-50 in.) 75-100 cm (30-40 in.) 50-75 cm (20-30 in.) 25-50 cm (10-20 in.) below-25 cm (0-10 in.) Ecological Diversity The variety of terrestrial and aquatic ecosystems found on the earth.
- 10. Science Focus: Insects • Around for ~400 million years • Bad reputations and hated! • Useful to humans and ecosystems • Vital roles in sustaining life: –Pollinators –Natural pest control –Renewing soils
- 11. How Does the Earth’s Life Change over Time? • The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. • Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).
- 12. Theory of Evolution • Fossils – Mineralized and petrified remains – Skeletons, bones, and shells – Leaves and seeds – Impressions in rocks – Fossil record incomplete: ~1% of all species • Charles Darwin, On the Origin of Species, 1859
- 13. Population Changes over Time • Populations evolve by becoming genetically different over time • Genetic variability – mutations: This produces variants e.g. SARS-CoV-2 Coronavirus variants in US, UK, SA etc. –Random changes in DNA molecules in genes –Can occur spontaneously –External agents: radiation –Can create a heritable trait
- 14. Natural Selection • Adaptive traits - genetically favorable traits that increase the probability to survive and reproduce • Trait – heritable and lead to differential reproduction • Faced with environmental changes – Adapt through evolution – Migrate – Become extinct
- 15. Evolution through Natural Selection Summarized • Genes mutate, individuals are selected & populations evolve such that they are better adapted to survive and reproduce under existing environmental conditions. • "Survival of the fittest“ - a phrase that originated from Darwin Evolution theory as a way of describing the mechanism of Natural Selection. • The biological concept of fitness is defined as reproductive success. In Darwinian terms it is best understood as "Survival of the form that will leave the most copies of itself in successive generations."
- 16. Most of the normal bacteria die The genetically resistant bacteria start multiplying Eventually the resistant strain replaces the strain affected by the antibiotic A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Resistant bacterium How antibiotic resistant bacteria evolve
- 17. Differential Reproductive Success Imagine a population of beetles: There is variation in traits. For example, some beetles are green and some are brown. There is differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. End result: The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.
- 18. Adaptation through Natural Selection Has Limits • Humans unlikely to evolve and have skin that’s not harmed by UV radiation 1. Desired trait must already be in the gene pool. 2. Must have high reproductive capacity so adaptive traits can be spread rapidly.
- 19. Three Myths about Evolution through Natural Selection Refuted 1. “Survival of the fittest” does not mean “survival of the strongest” 2. Organisms do not develop traits just because they would be useful e.g. giraffes and long necks 3. There is no grand plan of nature to create more perfectly adapted species – no trend toward genetic perfection
- 20. Science Focus: How Did Humans Become Such a Powerful Species? • Key adaptations – enabled us to modify environment – Opposable thumbs – Walk upright – Complex brains • Transmit ideas to others • Develop technologies to alter environment Technology dominates earth’s life support systems and Net Primary Production
- 21. How Do Geological Processes and Climate Changes Affect Evolution? • Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.
- 22. Plate Tectonics • Locations of continents and oceans determine earth’s climate • Movement of continents allow species to move and adapt • Earthquakes and volcanoes affect biological evolution by separating populations of a species and allowing new species to develop
- 23. Present 65 million years ago 135 million years ago 225 million years ago
- 24. Earth’s Long-Term Climate Changes • Cooling and warming periods: – affect evolution and extinction of species –Change ocean levels and area –Glaciers expanding and contracting –Climate changes • Opportunities for the evolution of new species • Many species become extinct
- 25. 18,000 years before present Modern day (August) Northern Hemisphere Ice coverage Legend Continental ice Sea ice Land above sea level
- 26. Science Focus: Earth is Just Right for Life to Thrive Why are the following assertion's crucial to life on Earth? • Life needs a temperature range that ensures that we have liquid water • Earth’s orbit: right distance from sun • Earth’s optimal gravity: keeps atmosphere • Favorable temperature range over earth history has promoted evolution and biodiversity • Favourable oxygen level in atmosphere
- 27. How Do Speciation, Extinction, and Human Activities Affect Biodiversity? • Human activities decrease the earth’s biodiversity by: 1) Causing the premature extinction of species and, 2) Destroying or degrading habitats needed for the development of new species.
- 28. Speciation • Speciation –One species splits into two or more species that can no longer breed and produce fertile offspring • Geographic isolation • Reproductive isolation
- 29. Spreads northward and southward and separates Arctic Fox Gray Fox Differentenvironmental conditions lead to different selective pressures and evolution into two differentspecies. Adapted to cold throughheavier fur, shortears, shortlegs,and shortnose. White fur matches snow for camouflage. Adapted to heatthrough lightweight fur and long ears,legs,and nose,which give off more heat. Northern population Southern population Early fox population
- 30. Science Focus: Changing Genetic Traits • Artificial selection – Selective breeding: crossbreeding varieties within same species to enhance desired traits – Grains, fruits, vegetables, dogs, other animals • Genetic engineering – Add, delete, or alter DNA segments – Add desirable genes from other species – New drugs, pest-resistant plants – Controversial e.g. Acceptance of GMO food.
- 31. Extinction (1) • Biological extinction - entire species gone • Local extinction - all members of a species in a specific area gone • Endemic species vulnerable to extinction • Background extinction • Speciation is generally more rapid than extinction
- 32. Extinction (2) • Mass extinction –Earth took millions of years to recover from previous mass extinctions • Balance between speciation and extinction determines biodiversity of earth • Humans cause premature extinction of species
- 33. Human Activities and Extinction • Cause premature extinction of species • This is a very big threat to biodiversity
- 34. What is Species Diversity and Why is it Important? • Species diversity is a major component of biodiversity • Species diversity tends to increase the sustainability of some ecosystems. • The higher the species diversity of an ecosystem, the more stable the ecosystem is.
- 35. Species Diversity • Species richness • Species evenness • Varies with geographic location • Species richness declines towards poles
- 36. Richness and Sustainability • Hypothesis –Does a community with high species diversity/richness have greater sustainability and productivity? • Research suggests “yes”
- 37. What Roles Do Species Play in an Ecosystem? • Each species plays a specific ecological role in an ecosystem called its niche. • Ecological niche is a term for the position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role in the ecosystem. • Niche - address and role of a species in an ecosystem
- 38. Ecological Niche (1) • Species occupy unique niches and play specific roles in an ecosystem • Includes everything required for survival and reproduction: – Water – Sunlight – Space – Temperatures – Food requirements
- 39. Ecological Niche (2) • Generalist species • Specialist species • Native species • Nonnative species –Spread in new, suitable niches
- 40. Louisiana heron wades into water to seize smallfish Black skimmer seizes smallfish at water surface Ruddy turnstone searches under shells and pebbles for small invertebrates Avocetsweeps bill throughmud and surfacewater in searchof small crustaceans,insects, and seeds Brown pelican dives for fish, which it locates from the air Dowitcherprobes deeply into mud in searchof snails, marine worms,and small crustaceans Herring gull is a tireless scavenger Flamingo feedson minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Piping plover feeds on insects and tiny crustaceans on sandy beaches Knot(sandpiper) picks up worms and small crustaceans left by recedingtide Oystercatcherfeeds on clams,mussels,and other shellfish into which it pries its narrow beak Fig. 4-10, p. 72
- 41. Science Focus: Why are Cockroaches very successful? • Existed for 350 million years - 3,500 known species (Compare: Human beings – only one species!) • Highly adapted, rapidly producing generalists – Consume almost anything – Endure food shortage – Survive everywhere except polar regions – Avoid predation • Carry human diseases
- 42. Indicator Species • A species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem. (They reflect the quality and changes in environmental conditions as well as aspects of community composition). • Early warning system e.g. Macroinvertebrates, fish, birds, butterflies, amphibians
- 43. Organ formation Eggs Sperm Sexual reproduction Fertilized egg development Egg hatches Tadpole Tadpole develops into frog Adult frog (3 years) Young frog
- 44. Keystone Species • A keystone species is an organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. • Significant role in their food web: large affect on types and abundances of other species in an ecosystem • Elimination may alter structure and/or function of ecosystem e.g. pollinators (bees), top predators. (sharks). • Top predator - a predator at the top of a food chain, without natural predators.
- 45. Position of Top Predators
- 46. Foundation Species • A foundation species/'Ecosystem Engineers' - any species that has a large contribution towards creating and maintaining habitats that support other species. • Create habitats and ecosystems • e.g. Beavers, Elephants, Seed dispersers
- 47. Science Focus: American Alligator – Why successful? • Highly adaptable • Only natural predator is humans • 1967 – endangered species list • Successful environmental comeback • Keystone species
- 48. Case Study: Why Should We Protect Sharks? • Remove injured, sick animals • Many are gentle giants • Provide potential insight into cures for human diseases such as cancer • Keystone species • Hunted and killed by humans for food
- 49. Three Big Ideas from This Lecture #1 • Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).
- 50. Three Big Ideas from This Lecture #2 • Human activities are decreasing the earth’s vital biodiversity by: (1) causing the premature extinction of species and (2) disrupting habitats needed for the development of new species.
- 51. Three Big Ideas from This Lecture #4 • Each species plays a specific ecological role in the ecosystem where it is found (ecological niche).
- 52. Asanteni Sana!