BIOE 109Summer 2009

Lecture 8- Part IAdaptation

http://www.naturefootage.com/video_clips/BF09_136

What is adaptation? 

What is adaptation?  

1. Acclimatization 

What is adaptation?  

1. Acclimatization 

• refers to the physiological adjustment of individual organisms to different conditions (e.g., temperature, photoperiod). NO genetic change.

  

What is adaptation?  

1. Acclimatization 

• refers to the physiological adjustment of individual organisms to different conditions (e.g., temperature, photoperiod). NO genetic change.

  

What is adaptation?  

1. Acclimatization 

• refers to the physiological adjustment of individual organisms to different conditions (e.g., temperature, photoperiod). NO genetic change.  

 

2. Adaptation

What is adaptation?  

1. Acclimatization 

• refers to the physiological adjustment of individual organisms to different conditions (e.g., temperature, photoperiod). NO genetic change.  

 

2. Adaptation• a trait that allows an individual to leave more offspring than it would if it lacked that trait

What is adaptation?  

1. Acclimatization 

• refers to the physiological adjustment of individual organisms to different conditions (e.g., temperature, photoperiod). NO genetic change.  

 

2. Adaptation• a trait that allows an individual to leave more offspring than it would if it lacked that trait

-Adaptations can be structural, behavioral or physiological.

Camouflage

The common cuttlefish (Sepia officinalis)

Cuttlefish crypsis

Feeding

Defenses

How do we study adaptations?  

There are three steps in carrying out the so-called “adaptationist program”:

1. Observe or describe some organismal trait.2. Formulate an adaptive hypothesis for the

evolution of that trait.3. Test hypothesis by experiment or by

collecting additional data.

How do we study adaptations?  

1. The experimental approach 

• hypotheses for the adaptive origins of traits are tested by experiments.  

How do we study adaptations?  

1. The experimental approach• hypotheses for the adaptive origins of traits are tested by experiments. 2. The observational approach 

How do we study adaptations?  

1. The experimental approach• hypotheses for the adaptive origins of traits are tested by experiments. 2. The observational approach• hypotheses for the adaptive origins or traits are tested by making observations within species

 

How do we study adaptations?  

1. The experimental approach• hypotheses for the adaptive origins of traits are tested by experiments. 2. The observational approach• hypotheses for the adaptive origins or traits are tested by making observations within species

3. The comparative approach 

How do we study adaptations?  

1. The experimental approach• hypotheses for the adaptive origins of traits are tested by experiments. 2. The observational approach• hypotheses for the adaptive origins or traits are tested by making observations within species

3. The comparative approach • hypotheses for the adaptive origins or traits are tested by performing comparisons among species 

The experimental approachStaring down your enemy…

Example: the tephritid fly, Zonosemata vittigera

http://www.youtube.com/watch?v=bjUlPJk6rsU

The experimental approach  

Example: the tephritid fly, Zonosemata vittigera  

Initial observations:  

The experimental approach  

Example: the tephritid fly, Zonosemata vittigera  

Initial observations:  

1. distinctive dark wing bands  

The experimental approach  

Example: the tephritid fly, Zonosemata vittigera  

Initial observations:  

1. distinctive dark wing bands 

2. wing-waving behavior   

The experimental approach  

Example: the tephritid fly, Zonosemata vittigera  

Initial observations:  

1. distinctive dark wing bands 

2. wing-waving behavior  

Initial hypothesis: 

• markings and behavior mimics jumping spiders thus deterring other predators.  

The experimental approach  

Example: the tephritid fly, Zonosemata vittigera  

Initial observations:  

1. distinctive dark wing bands 

2. wing-waving behavior  

Initial hypothesis: 

• markings and behavior mimics jumping spiders thus deterring other predators.  

Alternative hypothesis: 

• markings and behavior mimics jumping spiders to deter predation by jumping spiders. 

The experimental approach  

Question: 

The experimental approach  

Question: 

Do the traits actually mimic the threat display of the jumping spider thereby allowing the fly to escape predation?   

The experimental approach  

Question: 

Do the traits actually mimic the threat display of the jumping spider thereby allowing the fly to escape predation?   

Hypotheses: 

The experimental approach  

Question: 

Do the traits actually mimic the threat display of the jumping spider thereby allowing the fly to escape predation?   

Hypotheses: 

HO: Flies do not mimic jumping spiders (null hypothesis).   

The experimental approach  

Question: 

Do the traits actually mimic the threat display of the jumping spider thereby allowing the fly to escape predation?   

Hypotheses: 

HO: Flies do not mimic jumping spiders (null hypothesis).  

H1: Flies mimic jumping spiders to avoid other predators.  

The experimental approach  

Question: 

Do the traits actually mimic the threat display of the jumping spider thereby allowing the fly to escape predation?   

Hypotheses: 

HO: Flies do not mimic jumping spiders (null hypothesis).  

H1: Flies mimic jumping spiders to avoid other predators.  

H2: Flies mimic jumping spiders to avoid predation by jumping spiders. 

The experimental design

Experimental results

The observational approach  

Making observations within species

The observational approach  

Making observations within species

The observational approach  

Making observations within species – the polar bear

Observation: Polar bears are white!

The observational approach  

Making observations within species – the polar bear

Observation: Polar bears are white!

Hypothesis: Polar bears evolved a white coat as an adaptation to hunting in a white environment

The observational approach 

Making observations within species – the polar bear

Observation: Polar bears are white!

Hypothesis: Polar bears evolved a white coat as an adaptation to hunting in a white environment

Prediction: Polar bears should hunt in a manner that takes advantage of this camouflage

The observational approach  

Making observations within species – the polar bear

Stirling (1974) described the hunting strategies of 288 polar bears:

“sneak and pounce” “jump and crush” “sit and wait”

The obseravtional approach  

Making observations within species – the polar bear

Stirling (1974) described the hunting strategies of 288 polar bears:

1 “sneak and pounce”

The observational approach  

Making observations within species – the polar bear

Stirling (1974) described the hunting strategies of 288 polar bears:

1 “sneak and pounce” 54 “jump and crush”

The observational approach  

Making observations within species – the polar bear

Stirling (1974) described the hunting strategies of 288 polar bears:

1 “sneak and pounce” 54 “jump and crush” 233 “sit and wait”

The observational approach  

Making observations within species – the polar bear

Stirling (1974) described the hunting strategies of 288 polar bears:

1 “sneak and pounce” 54 “jump and crush” 233 “sit and wait”

Why then are polar bears white?

The observational approach  

Making observations within species – the polar bear

Observation: polar bears are black when photographed under UV light (i.e., the coat absorbs UV light)

The observational approach  

Making observations within species – the polar bear

Observation: polar bears are black when photographed under UV light (i.e., the coat absorbs UV light)

Hypothesis: Polar bears evolved a white coat to serve as a “solar heat collector”

The observational approach  

Making observations within species – the polar bear

Observation: polar bears are black when photographed under UV light (i.e., the coat absorbs UV light)

Hypothesis: Polar bears evolved a white coat to serve as a “solar heat collector”

How could this be tested?

Other explanations?

1. Sexual selection?

Other explanations?

1. Sexual selection?

2. Perhaps the initial advantage was camouflage?

The comparative approach  

Performing comparisons among species

The comparative approach: testes size in fruit bats & flying foxes

The comparative approach  

Performing comparisons among species

Observation: Testes size is highly variable among species.

  

The comparative approach  

Performing comparisons among species

Observation: Testes size is highly variable among species.

  

Hypothesis: Males have evolved large testes in some taxa due to sperm competition. 

The comparative approach  

Performing comparisons among species

Observation: Testes size is highly variable among species.

  

Hypothesis: Males have evolved large testes in some taxa due to sperm competition.  

Prediction: A positive relationship should exist between testes size and social group size.  

The comparative approach  

Performing comparisons among species

Observation: Testes size is highly variable among species.

  

Hypothesis: Males have evolved large testes in some taxa due to sperm competition.  

Prediction: A positive relationship should exist between testes size and social group size.  

(Assuming that sperm competition is more intense in larger social groups.) 

Relationship between testes size and social group size

A potential problem – lack of independence

Performing phylogenetically independent contrasts

After correcting for the phylogeny…

After correcting for the phylogeny…

YES!

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

• Cannot just accept a hypothesis because it is plausible.

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

• Cannot just accept a hypothesis because it is plausible.

• Have to test alternative explanations

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

• Cannot just accept a hypothesis because it is plausible.

• Have to test alternative explanations• Differences among species are not always

adaptive!

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

• Cannot just accept a hypothesis because it is plausible.

• Have to test alternative explanations• Differences among species are not always

adaptive • Not every adaptation is perfect

Adaptation Reminders

• Polar bear example= Must be careful in carrying out the adaptations program.

• Cannot just accept a hypothesis because it is plausible.

• Have to test alternative explanations• Differences among species are not always

adaptive • Not every adaptation is perfect• Not every trait of an organism is adaptive.

Adaptation questions:

• If a trait is not an adaptive trait how can it persist?

• Why certain populations (or species) do not possess certain traits that might be obviously advantageous for them in the given/ changing environment?

• If a trait is adaptive, is it always adaptive? Is the organism stuck with the trait forever?