Section ii evolution and behavioral ecology
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Section II Evolution and Behavioral Ecology. 鄭先祐 生態主張者 Ayo [email protected] Section Two Evolution and Behavioral Ecology. Chap.2 Genetics and Ecology ( 遺傳與生態 ) Chap.3 Extinction ( 滅絕 ) Chap.4 Group selection and individual selection Chap.5 Life History Strategies ( 生活史的策略 ).

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Section II Evolution and Behavioral Ecology

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Section ii evolution and behavioral ecology

Section IIEvolution and Behavioral Ecology

鄭先祐

生態主張者 Ayo

[email protected]


Section two evolution and behavioral ecology

Section Two Evolution and Behavioral Ecology

  • Chap.2 Genetics and Ecology (遺傳與生態)

  • Chap.3 Extinction (滅絕)

  • Chap.4 Group selection and individual selection

  • Chap.5 Life History Strategies (生活史的策略)

生態學 2003 Chap. 2 Genetics and Ecology


Chap 2 genetics and ecology

Road Map

Chap. 2 Genetics and Ecology

  • Species occurrence due to evolutionary past.

  • Mutations and chromosomal rearrangements result in a wide variety of species on earth.

  • Genetic variability can be measured by allozymes or DNA sequencing.

  • Mechanisms for reductions in genetic variability in populations.

生態學 2003 Chap. 2 Genetics and Ecology


2 1 evolutionary history

2.1 Evolutionary History

  • Importance of evolutionary ecology to the discipline.

  • Example: Control of penguins in the Southern Hemisphere vs. their absence in Northern Hemisphere.(企鵝只發現於南半球)

    • Penguins evolved in the Southern Hemisphere.

    • Unable to migrate to Northern Hemisphere

生態學 2003 Chap. 2 Genetics and Ecology


Evolutionary history

Evolutionary history

  • South America, Africa, and Australia

    • Similar climates (Tropical to temperate)

    • Characterized by different inhabitants.

  • South America: Ex. Sloths, anteaters, armadillos, and monkeys with prehensile tails.

  • Africa: Ex. Antelopes, zebras, giraffes, lions, baboons, okapi, and aardvark.

生態學 2003 Chap. 2 Genetics and Ecology


Characterized by different inhabitants

Characterized by different inhabitants

  • Australia: Ex. No native placental mammals except bats, variety of marsupials, egg-laying montremes, duck-billed platypus, and the echidna.

  • Best explanation of differences: Evolution.

生態學 2003 Chap. 2 Genetics and Ecology


2 2 genetic mutation

2.2 Genetic Mutation

  • Increase in number of species is primarily due to mutation.

  • Two types of mutation

    • Gene or point mutation

    • Chromosome mutation

生態學 2003 Chap. 2 Genetics and Ecology


Point mutation

Point mutation

  • Results from a misprint in DNA copying

    • Example (Figure 2.1)

  • Most changes are caused by frameshift mutations

    • An addition or deletion in the amino-acid sequence usually leads to drastic and often fatal mutations

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Direction of transcription

AGA

CGG

DNA

TGA

TTT

GCA

ACU

RNA

UCU

GCC

AAA

CGU

Protein

Ser

Thr

Ala

Lys

Arg

Frameshift: Insert T

Transition A-G

ATG

ACG

GTT

TGC

A..

GGA

DNA

TTT

GCA

DNA

AGT

TGA

CGG

UGC

CAA

ACG

UAC

CCU

RNA

RNA

UCA

ACU

GCC

AAA

CGU

Thr

Tyr

Glu

Ser

Cys

Pro

Protein

Ala

Thr

Lys

Arg

Protein

?

Fig. 2.1 Types of point mutation.

生態學 2003 Chap. 2 Genetics and Ecology


Chromosome mutation

Chromosome mutation

  • Four types: deletion, duplications, inversions, and translocation (Figure 2.2)

  • Deletion

    • Simple loss of part of a chromosome

    • Most common source of new genes

    • Often lethal

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

  • Duplication

    • Arises from chromosomes not being perfectly aligned during crossing over.

    • Results in one chromosome being deficient and the other one with duplication of genes.

    • May have advantages due to increased enzyme production.

  • Inversion

    • Occurs when a chromosome breaks in two places. When the segment between the two breaks refuses, it does so in reverse order.

    • Occurs during prophase.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Original

Breakage

Altered

A B C D E F G H

A B C D E F

G

H

A B C D E F H

Deletion

Eliminated

A B C D E F

G H

A B C D E F G G H

Duplication

From another

chromosome

G

E

A B G F E D C H

F

D

Inversion

G

C

H

A B

F G H

A B C D E T U V

A B C D E F G H

A B C D E

Translocation

O P Q R S T U V

O P Q R S

T U V

O P Q R S F G H

Fig. 2.2 Chromosome breakage and reunion.

生態學 2003 Chap. 2 Genetics and Ecology


Fig 7 15

Fig. 7.15

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Fig. 7.15

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Fig. 7.15

生態學 2003 Chap. 2 Genetics and Ecology


2 3 measuring genetic variability

2.3 Measuring Genetic Variability

  • Genetic diversity is essential to the breeding success of most populations.

  • Two individuals with the same form of enzyme are genetically identical at that locus.

  • Variations in gene loci are found through searching for variations in the enzymes (allozymes).

  • Gel electrophoresis: Technique for determining differences in allozymes.

  • Example of Gel electrophoresis: Figure 2.3.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Fig. 2.3 Researcher examines an agarose gel on which samples are separated according to migration rates during the application of an electric current.

生態學 2003 Chap. 2 Genetics and Ecology


Gene sequencing

Gene Sequencing

  • Another method for assessing variations is the sequence of DNA.

  • Made possible through the polymerase chain reaction (PCR) technique.

  • Made possible through the polymerase (cont.).

    • Makes millions of copies of a particular region of DNA, thereby amplifying even minute amounts of DNA.

生態學 2003 Chap. 2 Genetics and Ecology


Dna amplified

DNA amplified

  • DNA可以經由 polymerase chain reaction (PCR) 被 amplified (increased)。

  • 將片斷的DNA與nucleotides 和DNA polymerase混合。DNA polymerase可以促使DNA複製。

  • DNA將會持續複製到nucleotides耗盡。速度相當快。於幾個小時內,就可以有1,000億個copies(DNA)。 (Fig.8.3)

教科書:Wallace, R. A. (1997) Biology: the world of life. Addison Wesley Longman, Inc.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Fig. 8.3 DNA片斷 複製增加的方法。經過25個周期,就可以有1,000,000個copies。

教科書:Wallace, R. A. (1997) Biology: the world of life. Addison Wesley Longman, Inc.

生態學 2003 Chap. 2 Genetics and Ecology


Mutation

Mutation

  • Accelerated through human-made radiation, UV light, or other mutagens.

  • Rate of occurrence: one per gene locus in every 100,000 sex cells. Only one out of 1,000 mutations may be beneficial.

  • Estimated that only 500 mutations would be expected to transform one species into another.

  • Rate of mutation is not the chief factor limiting the supply of variability.

  • Variability is mainly limited by gene recombination and the structural patterns of chromosomes.

生態學 2003 Chap. 2 Genetics and Ecology


2 4 genetic diversity and population size

2.4 Genetic Diversity and Population Size

  • Function of population size

  • Four factors:

    • inbreeding,

    • genetic drift,

    • Neighborhoods,

    • Effective population size

生態學 2003 Chap. 2 Genetics and Ecology


Inbreeding depression

Inbreeding Depression

  • Mating among close relatives.

  • Reduced survivorship (Figure 2.4).

  • Various types of inbreeding (Figure 2.5)

  • inbreeding on juvenile mortality (fig. 2.6)

  • inbreeding on small populations (Figure 2.7).

  • Greater Prairie Chicken (Figures 2.8 and 2.9).

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

60

Non-productive

matings

50

Mortality from

birth to four

weeks

40

Percent

30

20

10

0

1 2 3 4 5 6

Years

Fig. 2.4 inbreeding in rats.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

1.0

A: exclusive self-fertilization

B: sibling mating

C: double-first-cousin mating

0.8

C

0.6

B

Fraction of initial genetic variation

0.4

A

0.2

15

20

0

10

5

Generations

Fig. 2.5 The decrease in genetic variation is faster the greater the inbreeding.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Saddle back tamarin

70

Ungulates

Primates

60

Small Animals

50

Macaque

40

Chimpanzee

% Juvenile mortality- outbred

Lemur

30

Giraffe

20

Eld’s deer

Indian elephant

Rat

10

Spider monkey

Oryx

Mandrill

Mouse

0

100

80

20

40

60

% Juvenile mortality-inbred

Fig. 2.6 The effects of inbreeding on juvenile mortality in captive populations of mammals.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

1.0

N=1000

0.9

0.8

N=300

0.7

0.6

N=100

0.5

Fraction of initial genetic variation

N=20

0.4

0.3

0.2

0.1

200

400

300

100

500

0

Fig. 2.7 finite population size

Generations

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Eggs hatched

100

200

75

150

Prairie chicken cocks

Number of prairie chicken cocks

Eggs hatched (%)

50

100

25

50

Fig.2.9 decrease in hatching of prairie chicken eggs.

10

0

1973

1980

1990

Year

生態學 2003 Chap. 2 Genetics and Ecology


Greater prairie chicken

Greater prairie chicken

  • 1933, population size is 25,000

  • 1962, population size is 2,000

  • 1990, population size is 76

  • Less than 50 in 1994

  • Prairie chicken habitat was restored in 1970s and hunting had been banned since the 1940s.

生態學 2003 Chap. 2 Genetics and Ecology


Inbreeding and extinction

Inbreeding and extinction

  • Glanville fritillary butterfly (Figure 2.10)

  • Exists in numerous small, isolated local populations in meadows where the caterpillars feed on one or two host plants.

  • Seven of the 42 populations studied became extinct between 1995 and 1996; all seven had a lower population size and genetic variation than the survivors.

生態學 2003 Chap. 2 Genetics and Ecology


Genetic drift

Genetic Drift

  • Probability of the failure to mate

    • Loss of possible rare gene

    • Loss of genetic information for subsequent generations resulting in a loss of genetic diversity.

    • Small populations more susceptible to drift.

    • The rate of loss of original diversity over time is approximately equal to 1/2N per generation.

    • Example: N = 500 , then 1/2N = 0.001 or 0.1% genetic diversity lost per generation.

    • N = 50, then 1/2N = 0.01 or 1% genetic diversity lost per generation.

生態學 2003 Chap. 2 Genetics and Ecology


Probability of the failure to mate

Probability of the failure to mate

  • Over 20 generations, the population of 500 will still retain 98% of the original variation, but the population of 50 will only retain 81.79%.

  • 50/500 Rule: Need 50 individuals to prevent excess inbreeding and 500 is the critical size to prevent genetic drift.

生態學 2003 Chap. 2 Genetics and Ecology


Genetic drift1

Genetic drift

  • Effects of immigration on genetic drift (Figures 2.11 and 2.12).

  • Even the relatively low rate of one immigrant every generation would be sufficient to counter genetic drift in a population of 120 individuals.(Fig. 2.11)

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

Number of

immigrants per

generation

100

5

2

90

1

Percentage of initial

genetic variation remaining

80

0.5

70

0.1

60

None

50

10

20

30

40

50

60

70

80

90

100

Generation

Fig. 2.11 The effect of immigration on genetic variation in 25 simulated population of 120 individuals each. Even the low rate of one immigrant per generation can prevent the loss of heterozygosity through genetic drift.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

100

N = 101 or more

80

N = 51-100

N =16-30

60

Percentage of populations persisting

N = 31-50

40

N = 15 or less

20

0

10

20

30

40

50

Time (years)

Fig. 2.12

生態學 2003 Chap. 2 Genetics and Ecology


Neighborhoods and effective population size

Neighborhoods and Effective Population Size

  • Effective population size is determined on mating range.

  • Individuals may only mate within their neighborhood.

  • Example: Deer mice. 70% of the males and 85% of the females breed within 150m of their birthplaces.

生態學 2003 Chap. 2 Genetics and Ecology


Harem effects

Harem Effects

  • Even within a neighborhood, some individuals may not reproduce.

  • In a harem structure, only a few dominant males breed.

生態學 2003 Chap. 2 Genetics and Ecology


Effective population size

Effective Population Size

  • NE = (4 Nm Nf) / (Nm + Nf).

  • Where:

    • NE = Effective Population Size;

    • Nm = Number of Breeding Males;

    • Nf = Number of Breeding Females.

生態學 2003 Chap. 2 Genetics and Ecology


Effective population size1

Effective Population Size

  • A population of 500 with a 50:50 sex ratio and all individuals breeding.

    • NE = (4 x 250 x 250) / (250+250) = 500

  • If 250 females bred with 10 males.

    • NE = (4 x 10 x 250) / (10 +250) = 38.5

    • Only 7 percent of the actual population size.

生態學 2003 Chap. 2 Genetics and Ecology


Can cloning help save endangered species

Applied Ecology

Can Cloning help save endangered species?

  • Dolly, the cloned sheep – Ian Williams 1997 (Photo 1).

  • Need knowledge of reproductive cycle.

  • Need for surrogate females.

  • Expense associated with cloning.

  • Can not address genetic diversity.

生態學 2003 Chap. 2 Genetics and Ecology


Section ii evolution and behavioral ecology

  • 問題與討論!

[email protected]

Ayo 台南站: http://mail.nutn.edu.tw/~hycheng/

生態學 2003 Chap. 2 Genetics and Ecology


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