Population evolution

1. Population evolution

2. Size • Density • Dispersion Properties of Population

3. Fundamental and important property of population but can be difficult to measure directly. • Often too abundant, mobile, or widespread to count. Population size

4. Population density is the quantity of individuals living in a particular space. Population Density

5. Population Dispersion

6. What would the data table for this look like? Population ProfileAKA: Age Structure

7. Type 1 What does each line say about the population? Type 2 Type 3 Survivorship curves Relative Age

8. Type 1: ex: humans: chances of death increase with age. • Type 2: ex: certain species of birds: probability of mortality does not change through out the lifespan. • Type 3: ex: sea turtles: chance of death is higher at younger ages. If they make it past this stage they stand a good chance to make it to old age. Survivorship curve

9. Measuring Populations 19.2

10. Growth = births – deaths • Increased life expectancy: childhood immunizations, vaccines, medications that prevent/maintain things like heart disease and diabetes, improved health care, etc. • This formula doesn’t take into account another factor of population growth: Immigration and emigration. • Mortality=death Population Influences

11. As long as births > deaths the population will grow • Even once births < deaths the population will take time to level off or decrease because of the base number of individuals who are of reproductive age. • Population also grows faster if the start of reproduction is at earlier ages. • Once the environment reaches the maximum number of individuals it can support (K=carrying capacity)the population will level off. • Not true of human populations…they make choices and can therefore change the dynamics of the graph. Exponential Population Growth

12. Any factor such as space which will limit the growth of an organism • All populations are ultimately limited by their environment. • The logistic growth model is similar to the exponential growth model except that it accounts for liming factors (carrying capacity=K) Limiting factor

13. Exponential growth curve K Logistic growth curve Limiting factor Exponential growth with and without “K”

14. Predator populations follows close pattern to prey. • If a new organism (for example another predator that is capable of eating the same prey) were artificially added the natural predator can be affected as can the prey population. • The new predator may eat more or less either dwindling the prey or causing it to “grow” out of control. Population Fluctuations

15. Density independent: Reduce the population by the same amount regardless of the size of the population • Fire, flood, weather. • Density dependent: an individual’s chance of surviving or reproducing depends on the number of individuals in the area. • Resources such as food, nesting space. Density Dependence

16. Small populations are more likely to be affected or even wiped out by such natural disasters as floods, fires, storms, or disease outbreaks. • Can lead to too few individuals to maintain the population. California Condor Perils of small populations

17. Human Population Growth 19.3

18. What scientists learned from this time period: • Small populations and high mortality rates lead to slow growth. • High infant and childhood mortality are especially high factors in slowing population growth because they never make it to reproductive age. Hunter/Gatherer Period

19. What happened during this period? • Agriculture greatly increased and stabilized food supplies. • Human populations began to grow faster. • People had more children • Needed more hands to work the farm • They weren’t as mobile so it made it easier to have more children. Agricultural revolution

20. After 1650: • Sharp decline in death rates because of improved sanitation, hygiene, control of disease, increased availability of food. • Birth rates remained high. Industrial Revolution

21. Environmental Issues Chapter 22 Section 2

22. What does this graph tell you? • Shows a correlation between CO2 and global warming. • Shows the concentration of CO2 in the atmosphere from 1880-2000. Global Warming

23. Biological Magnification

24. Evolution Lesson 15.1

25. Supported the idea that populations changed over time, but thought that acquired changes would be carried to the next generation. • Does a deer who looses an antler in a fight with another deer pass that “lost antler” trait on to the next generation? • Lemarck thought it did. • He also thought that individuals could acquire traits within their lifetime due to experience or behavior. • If you need fins, are you going to grow them? Lemarck

26. Proposed the theory of Natural selection • Organisms may possess traits that make them more suitable to their environment. Those individuals survive, pass on those traits to future generations. (survival of the fittest) • Requires genetic variation within a species. • Is the process that leads to evolution (natural selection over many generations) Darwin

27. Disruption of Genetic Equilibrium Lesson 16.2

28. Possible causes of disrupted genetic equilibrium: • Mutation • Immigration/emigration (migration) • Genetic drift • Traits change as a result of random events or chance • Happens more in smaller populations than in larger ones. • Artificial selection • Nonrandom mating • Small population size Causes of evolution

29. Many times mate selection is determined by geographic proximity. • May result in disorders caused by inbreeding. • Sometimes a mate is chosen because they possess similar traits: assortative mating. • Sexual Selection: In order to be selected by a mate, and leave offspring, an individual must possess extreme traits (like the plumage of a peacock) Nonrandom Mating

30. The “average” individual is best fit. • Consider the hypothetical situation of the lizard…Large ones may be more easily seen by predators, while small sized ones may be to slow to escaper predators…therefore it is the average sized individuals which may be best suited to the environment. Stabilizing Selection

31. Individuals with the extreme variation of a trait have a greater chance of survival than the one with the average variation. • Therefore individuals with short fat beaks and those with long narrow beaks would survive, but those with average length beaks die out on an island with flowers and nuts. Disruptive Selection

32. Individuals that display a more extreme form of a trait have greater fitness than an individual with an average trait. • For example when anteaters feed, they push their sticky tongue into the nest of termites. The longer the tongue the more fit the anteater. Directional selection

34. Formation of Species Lesson 16.3

35. The process of species formation that results in closely related species. • Some are very similar to their shared ancestor. Speciation

36. Proposed by Mayr, a species is an interbreeding population that cannot breed with other groups. Biological Species Concept

37. Geographic Isolation: Physical separation of members of a population. • When the original habitat becomes physically separated. • Reproductive Isolation: May sometimes arise through disruptive selection where the two extremes are selected for and as time passes, the two subpopulations can no longer interbreed. Isolation and Speciation

38. Gradualism: speciation occurs at a regular, gradual rate. • Punctuated equilibrium: Speciation occurs at a rapid pace. • What is rapid in evolution? • A few thousand years rather than a few million. Rates of Speciation

39. Two or more species become adapted to each other’s presence over a period of time Coevolution

40. Divergent: one species becomes two separate subpopulations. • Artificial selection has been used by humans to speed up this process. • Convergent: two species develop similarities even though they come from two very different ancestors.