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Evolution and Biodiversity

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1 Evolution and Biodiversity
Chapter 4 Evolution and Biodiversity

2 Chapter Overview Questions
How do scientists account for the development of life on earth? What is biological evolution by natural selection, and how can it account for the current diversity of organisms on the earth? How can geologic processes, climate change and catastrophes affect biological evolution?

3 Chapter Overview Questions (cont’d)
What is an ecological niche, and how does it help a population adapt to changing environmental conditions? How do extinction of species and formation of new species affect biodiversity?

4 Chapter Overview Questions (cont’d)
What is the future of evolution, and what role should humans play in this future? How did we become such a powerful species in a short time?

5 Review: 4 Principles of Sustainability?
1. 2. 3. 4.

6 Core Case Study: Why Should We Care about the American Alligator?
Hunters wiped out population to the point of near extinction. 1967- classified as endangered 1975- numbers had rebounded 1977- reclassified as threatened Figure 7-1

7 Core Case Study: Why Should We Care about the American Alligator?
Alligators have important ecological role. Alligators are a keystone species: Influence on ecosystem is much greater than their numbers would suggest Figure 7-1

8 Core Case Study: American Alligator as Keystone Species
Dig deep depressions (gator holes). Hold water during dry spells, serve as refuges for aquatic life. Build nesting mounds. provide nesting and feeding sites for birds. Keeps areas of open water free of vegetation (swimming paths) Keep gar populations in check

9 Gator Holes

10 Nesting Mounds

11 Keep Waterways Clear

12 Longnose Gar

13 Alligator Gar

14 Core Case Study Earth: The Just-Right, Adaptable Planet
Distance from sun Spins Size- molten mantle, retain atmosphere Stratospheric Ozone (2 billion years) 21% Oxygen (several hundred million years) Biodiversity & Sustainability Temp Figure 4-1

15 Core Case Study Earth: The Just-Right, Adaptable Planet
During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC. Figure 4-1

16 Biological Evolution This has led to the variety of species we find on the earth today. Figure 4-2

17 Recorded human history begins about 1/4 second before midnight
Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight Recorded human history begins about 1/4 second before midnight Age of mammals Age of reptiles Insects and amphibians invade the land Origin of life ( billion years ago) Figure 4.3 Natural capital: greatly simplified overview of the biological evolution by natural selection of life on the earth, which was preceded by about 1 billion years of chemical evolution. Microorganisms (mostly bacteria) that lived in water dominated the early span of biological evolution on the earth, between about 3.7 billion and 1 billion years ago. Plants and animals evolved first in the seas. Fossil and recent DNA evidence suggests that plants began invading the land some 780 million years ago, and animals began living on land about 370 million years ago. Humans arrived on the scene only a very short time ago—equivalent to less than an eye blink of the earth’s roughly 3.7-billion-year history of biological evolution. First fossil record of animals Plants begin invading land Evolution and expansion of life Fig. 4-3, p. 84

18 How Do We Know Which Organisms Lived in the Past?
Our knowledge about past life comes from fossils cores drilled out of buried ice analysis of protein similarities DNA & RNA analysis. Figure 4-4

Evolution in Seven Words: Genes Mutate, Individuals are Selected, Populations Evolve

20 Natural selection acts on individuals, but evolution occurs in populations
Three conditions are necessary for biological evolution: 1. Genetic variability traits must be heritable 3. trait must lead to differential reproduction. An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations. With positive selection pressure, advantageous traits help individuals to survive long enough to have and raise their young. With negative selection pressure, individuals die before they can reproduce.

Advantageous traits originate from genetic variability. Genetic variability occurs through… mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring. Exposure to mutagens: radioactivity, x rays, certain chemicals Random mistakes in DNA duplication, or during RNA transcription and translation.

23 Limits on Adaptation through Natural Selection
A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

24 Common Myths about Evolution through Natural Selection
Yes: Biological evolution through natural selection is about the most descendants. No: (Misunderstandings) “Survival of the fittest” means “survival of the biggest, fastest, or strongest”. Organisms develop certain traits because they need them. Species evolve towards genetic perfection.

25 New Species: Hybridization
New species can arise through hybridization. Occurs when individuals to two distinct species crossbreed to produce a fertile offspring. The red wolf is thought to be a coyote/wolf hybrid

26 New Species: Gene Swapping
Some species (mostly microorganisms) can exchange genes without sexual reproduction. Horizontal gene transfer


28 Why Should We Care About Biodiversity?
Some consider it ethical to care about nature. Biodiversity provides us with: Natural Resources (food, water, wood, energy, and medicines) Natural Services (air and water purification, soil fertility, waste disposal, pest control) Aesthetic pleasure

29 Biodiversity Loss and Species Extinction: Remember HIPPO
H for habitat destruction and degradation I for invasive species P for pollution P for human population growth O for overexploitation

Smooth cordgrass, Spartina alterniflora, Can grow in fresh water… …but it doesn’t in the wild. Why not?

Each species in an ecosystem has a specific role or way of life. Fundamental niche: the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use. Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

32 Species Diversity and Niche Structure: Different Species Playing Different Roles
Biological communities differ in the types and numbers of species they contain and the ecological roles those species play. Species diversity has 2 components: species richness the number of different species the ecosystem contains species evenness the abundance of individuals within each of those species.

33 Species Diversity and Niche Structure
Niche structure: how many potential ecological niches occur, how they resemble or differ, and how the species occupying different niches interact. Geographic location: species diversity is highest in the tropics and declines as we move from the equator toward the poles.

34 TYPES OF SPECIES Native, nonnative, indicator, keystone, and foundation species play different ecological roles in communities. Native: those that normally live and thrive in a particular community. Nonnative species a.k.a. invasive species: those that migrate, deliberately or accidentally introduced into a community.

35 Indicator Species: Biological Smoke Alarms
Species that serve as early warnings of damage to a community or an ecosystem. “Canary in a coal mine” Presence or absence of trout species because they are sensitive to temperature and oxygen levels. Birds- require a range of habitat Lichens- stay in one place and absorb from the environment Amphibians- vulnerable at any part of life cycle

36 Case Study: Why are Amphibians Vanishing?
Frogs serve as indicator species because different parts of their life cycles can be easily disturbed. Next

37 Adult frog (3 years) Young frog Sperm Tadpole develops into frog
Sexual Reproduction Tadpole Figure 7.3 Typical life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting for food (frog legs), and nonnative predators and competitors. Eggs Fertilized egg development Egg hatches Organ formation Fig. 7-3, p. 147

38 Case Study: Why are Amphibians Vanishing?
Habitat loss and fragmentation. Prolonged drought. Increases in ultraviolet radiation. Parasites. Viral and Fungal diseases. Overhunting. Air OR water pollution Natural immigration or deliberate introduction of nonnative predators and competitors.

39 Keystone Species: Major Players
Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it. Figures 7-4 and 7-5

40 Foundation Species: Other Major Players
Expansion of keystone species category. Foundation species can create and enhance the physical habitats to benefit other species in a community. Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize. Alligators making “gator holes”

41 Generalist and Specialist Species: Broad and Narrow Niches
Generalist species tolerate a wide range of conditions. Specialist species can only tolerate a narrow range of conditions. Exp: tiger salamander, giant panda Figure 4-7

42 Specialist species Generalist species with a narrow niche
with a broad niche Niche separation Number of individuals Figure 4.7 Overlap of the niches of two different species: a specialist and a generalist. In the overlap area, the two species compete for one or more of the same resources. As a result, each species can occupy only a part of its fundamental niche; the part it occupies is its realized niche. Generalist species such as a raccoon have a broad niche (right), and specialist species such as the giant panda have a narrow niche (left). Niche breadth Region of niche overlap Resource use Fig. 4-7, p. 91

43 SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors
350 million years old 3,500 different species Ultimate generalist Can eat almost anything. Can live and breed almost anywhere. Can withstand massive radiation. Figure 4-A

44 Specialized Feeding Niches
Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8

45 Avocet sweeps bill through mud and surface water in
search of small crustaceans, insects, and seeds Ruddy turnstone searches under shells and pebbles for small invertebrates Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Black skimmer seizes small fish at water surface Louisiana heron wades into water to seize small fish Figure 4.8 Natural capital: specialized feeding niches of various bird species in a coastal wetland. Such resource partitioning reduces competition and allows sharing of limited resources. Piping plover feeds on insects and tiny crustaceans on sandy beaches Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Knot (a sandpiper) picks up worms and small crustaceans left by receding tide (Birds not drawn to scale) Fig. 4-8, pp

46 Evolutionary Divergence: Darwin’s Finches
Each species has a beak specialized to take advantage of certain types of food resource. Next

47 Insect and nectar eaters
Fruit and seed eaters Insect and nectar eaters Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak Crested Honeycreeper Akiapolaau Figure 4.9 Natural capital: evolutionary divergence of honeycreepers into specialized ecological niches. Each species has a beak specialized to take advantage of certain types of food resources. Maui Parrotbill Apapane Unknown finch ancestor Fig. 4-9, p. 91

The movement of solid tectonic plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones. The locations of continents and oceanic basins influence climate. The movement of continents have allowed species to move.

49 225 million years ago 135 million years ago 65 million years ago
Figure 4.5 Geological processes and biological evolution. Over millions of years the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species as land areas split apart and promote the rise of new species when once isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s huge plates separated and eventually resulted in today’s locations of the continents (bottom right). 65 million years ago Present Fig. 4-5, p. 88

50 Climate Change and Natural Selection
Changes in climate throughout the earth’s history have shifted where plants and animals can live. Next

51 Northern Hemisphere Ice coverage
18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Note: Modern sea ice coverage represents summer months Legend Continental ice Figure 4.6 Changes in ice coverage in the northern hemisphere during the past 18,000 years. (Data from the National Oceanic and Atmospheric Administration) Sea ice Land above sea level Fig. 4-6, p. 89

Speciation: A new species can arise when member of a population become isolated for a long period of time. Due to natural selection over time, the genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.

53 Catastrophes and Natural Selection
Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

54 Geographic Isolation…
…can lead to reproductive isolation, which leads to divergence of gene pools and speciation. Figure 4-10

55 matches snow for camouflage.
Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage. Arctic Fox Northern population Early fox Population Spreads northward and southward and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern Population Figure 4.10 Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation. Gray Fox Fig. 4-10, p. 92

56 Extinction: Lights Out
Extinction occurs when the population cannot adapt to changing environmental conditions. The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11

57 Categorizing Extinction Rates
Biologists estimate that 99.9% of all the species that ever existed are now extinct. Background extinction- a certain number of species disappearing at a slow rate due to changes of local environmental conditions Estimate: 1-5 species per million per year Mass depletion- rates of extinction above background level but not high enough to be considered a mass extinction. Mass extinction- a significant rise in extinction rate above background level.

58 Effects of Humans on Biodiversity
The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13

59 Silurian Permian Jurassic Cambrian Ordovician Devonian Devonian
Terrestrial organisms Silurian Permian Jurassic Cambrian Ordovician Devonian Devonian Cretaceous Pre-cambrian Marine organisms Carboniferous Number of families Tertiary Quaternary Figure 4.13 Natural capital: changes in the earth’s biodiversity over geological time. The biological diversity of life on land and in the oceans has increased dramatically over the last 3.5 billion years, especially during the past 250 million years. During the last 1.8 million years this increase has leveled off. Millions of years ago Fig. 4-13, p. 94

60 Species and families experiencing mass extinction
Bar width represents relative number of living species Millions of years ago Era Period Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Quaternary Today Cenozoic Tertiary Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Mesozoic Jurassic Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 180 Triassic Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 250 Permian Carboniferous Extinction 345 Figure 4.12 Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Paleozoic Silurian Ordovician Extinction 500 Ordovician: 50% of animal families, including many trilobites. Cambrian Fig. 4-12, p. 93

We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding. We have used genetic engineering to transfer genes from one species to another (gene splicing) Takes half the time and costs less than crossbreeding. Figure 4-15

62 Genetic Engineering: Genetically Modified Organisms (GMO)
GMOs use recombinant DNA genes or portions of genes from different organisms. Figure 4-14

63 Case Study: Species Diversity on Islands
MacArthur and Wilson proposed the species equilibrium model a.k.a. theory of island biogeography in the 1960’s. Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on: Island size Distance to nearest mainland

Biologists are learning to rebuild organisms from their cell components and to clone organisms. Cloning has lead to high miscarriage rates, rapid aging, organ defects. Genetic engineering can help improve human condition, but results are not always predictable. Currently: We do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism.

65 Biopharming Biopharming is when humans use genetically engineered organisms for the production of consumables such as Drugs Chemicals Human body parts Which one of these have we not yet mastered?

66 Controversy Over Genetic Engineering
There are a number of privacy, ethical, legal and environmental issues. Should genetic engineering and development be regulated? What are the long-term environmental consequences?

67 Case Study: How Did We Become Such a Powerful Species so Quickly?
Compared to other species, we lack: strength, speed, agility. weapons (claws, fangs), protection (shell). poor hearing and vision. We have thrived as a species because of our: opposable thumbs ability to walk upright complex brains (problem solving).

68 Ch 4 Final Thoughts Microevolution- Traits changing in a species (e.g.color, fur type, etc.) Industrial Melanism in pepper moths: Macroevolution- The development of new species

69 Ch 4 Final Thoughts Gradualism- species change slowly over time at a steady rate of change (Darwin was wrong about this) Punctuated Equilibrium- Long periods of stability punctuated by peiods of rapid change, initiated by changes in the environment (evolutionary biologist Stephen Jay Gould) # of species Time # of species Time

70 Ch 4 Final Thoughts Natural Selection happens to individuals, and leads to differential reproduction (think about the wooly worms lab) Evolution happens to a population over time, and is ultimately understood as changes in gene frequencies within that population. Leads to microevolution in the short term Leads to macroevolution in the long term

71 Genetic Engineering: Genetically Modified Organisms (GMO)
GMOs use recombinant DNA genes or portions of genes from different organisms. Figure 4-14

72 Identify and remove portion of DNA with
Phase 1 Make Modified Gene E. coli Genetically modified plasmid Insert modified plasmid into E. coli Cell Extract Plasmid Extract DNA Plasmid Gene of interest DNA Identify and remove portion of DNA with desired trait Remove plasmid from DNA of E. coli Insert extracted (step 2) into plasmid (step 3) Identify and extract gene with desired trait Grow in tissue culture to make copies Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Fig. 4-14, p. 95

73 Transfer plasmid copies to a carrier agrobacterium
Phase 2 Make Transgenic Cell A. tumefaciens (agrobacterium) Foreign DNA E. Coli Host DNA Plant cell Nucleus Transfer plasmid copies to a carrier agrobacterium Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Transfer plasmid to surface of microscopic metal particle Use gene gun to inject DNA into plant cell Fig. 4-14, p. 95

74 Grow Genetically Engineered Plant
Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Transfer to soil Transgenic plants with new traits Fig. 4-14, p. 95

75 Grow Genetically Engineered Plant
Transgenic cell from Phase 2 Phase 3 Grow Genetically Engineered Plant Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Stepped Art Fig. 4-14, p. 95

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