NOT EXAM labs 1-3 + appendix A Flashcards
Adaptation
traits that contribute to an organism’s fitness by increasing its chance of surviving and reproducing
Can be physical feature of body (colour of wings) or behaviour (attraction to certain smells)
Not all traits are adaptations
E.g. reduviid bugs (nymphs) have an adaptation that covers their thorax with a layer of dust or sand which allows dead insects to stick to them and camouflages them from predators → increases their chance of survival
New traits and new combinations of traits are created in the population by ________(genetic errors) as well as ______________(mixing of genes through sex)
mutations ; recombination
fitness
Fitness can be measured as the number of offspring an individual produces relative to other individuals in the population
In order for a trait to evolve by natural selection, the following three criteria must be met:
The trait is heritable
There is variation between individuals within a population for the trait
Variation in the trait leads to some individuals leaving more offspring in the next gen than others (i.e. some individuals have higher fitness than others)
Population can also change genetically by random processes (_________) or by the influx of migrants from other populations (________)
genetic drift; gene flow
Adaptations for competition for mates
An individual’s fitness depends not only on how long it survives and how well it locates food, but also on how successful it is in competing for mates
An individual that fails to mate will produce no offspring and have a fitness of zero
sexual selection
Natural selection arising from variable mating success is called sexual selection
Sexual selection often results in the evolution of differences between males and females in secondary sexual characteristics (characteristics other than ovaries and testes)
sexual dimorphism
Differences in the shape or size of body called sexual dimorphism
Two principal mechanisms of sexual selection are
intrasexual competition and mate choice
Intrasexual competition
Males fight with other males for access to females
Males that defeat their rivals will sire more offspring (so they possess more adaptations for fighting - horns, tusks)
mate choice
In many species, females/males are choosy about their mates
Thought to increase the fitness of the “chooser” by enabling it to mate only with healthy individuals (which are thus more “attractive” as mates)
Attractive individuals attract more mates → produce more offspring
Adaptations include elaborate structures, colour patterns and courtship displays that might reveal their health and vigour
Phenotype plasticity →
a single genotype can produce different phenotypes in response to its environment
phenotype
The phenotype is the “outward appearance” or observable manifestation of a specific genotype
overall organism’s phenotype composed of its …
morphological, behaviour and physiology
When variation in the phenotype is observed within a population, the observed variation may result from variation among genotypes (i.e. genetic variation), the environment, or the interactions of both components
Evolution depends on ________ traits being passed down from gen to gen
phenotypic
-It’s an organism’s alleles and not its phenotype that are transmitted directly from parents to offspring
Continuous phenotypic traits are the result of…
interactions between multiple genes and the environment
Continuous phenotypic traits–>height/skin colour)
continuous phenotypic traits
Each of these genes can have a large or small effect on phenotypic expression
These traits referred to as quantitative or polygenic traits
(height, skin colour)
Because both gene expression and fitness are dependent on __________, an individual’s ability to respond to environmental conditions in a way that will increase its ________is an important factor in evolution
the environment; fitness
Individuals that can exploit the appropriate combination of phenotype and environment will gain the ________
Can be achieved by altering the environment (move to suitable habitat) or altering the _______–
highest fitness; phenotype
acclimation
Alteration of the phenotype, called acclimation, occurs in individuals that are able to modify their phenotype in response to environmental variation in a manner that improves fitness
Individuals don’t adapt but they ______to their environment
________are capable of adapting to changing environments
acclimate ; Populations
phenotype plasticity
When an individual can alter the expression of a phenotypic trait in response to the environment, they are showing phenotypic plasticity for that trait
Ability of one genotype to produce different phenotypes in different environments
Expresses itself as either discrete alternate types or in a continuum
E.g. desert annual plant produces either yellow(dormant) or green(non-dormant) seeds depending upon day length
When phenotype plasticity expresses itself in a continuum, the relationship between the environment and the trait in question is known as a …
reaction norm
Why aren’t all traits phenotypically plastic?
Possible explanation is that insufficient genetic variation exists(in species or trait) for the evolution of plasticity to occur
-even if sufficient variation exists for the evolution of plasticity, costs and limitations may result in a selective pressure against a trait evolving phenotypic plasticity
-costs associated with producing new phenotypes and maintaining the sensory and regulatory mechanisms required for plasticity may offer a significant selection pressure against the evolution of plasticity for a trait
-at a genetic level, linkage between genes might produce a situation whereby genes promoting plasticity might be linked to genes conferring a low fitness for other traits
limitation with producing new phenotypes
A limitation associated with producing new phenotypes is the accuracy with which an organism can correctly process environmental cues in order to appropriately acclimate
maladapted phenotype
If an organism incorrectly senses the environment, or the environment changes rapidly, the organism may produce a maladapted phenotype
Another limitation is the time difference between …
sensing environmental change and alteration of the phenotype
During this time, the organism will experience reduced fitness as it is not yet acclimated to its new environmental conditions
The greater the change in phenotype, the longer the time lag
What could lead to selection for the plasticity of a trait?
One example could be in heterogeneous environments, which change frequently over space/time
An individual that can produce more than one phenotype is more likely to acclimate to the changing conditions than an individual who can express only 1
Mechanism behind plastic response
Light is a critical resource for plant growth and survival, and leaves are designed to capture light
Example of phenotypic plasticity in plants is the adaptation of leaves to sun and shade conditions
How can a plant tell whether it will grow in the sun or shade?
Plants produce proteins called phytochrome, a photoreceptor that detects shading by other plants
As white light passes through a plant’s leaves, some wavelengths are absorbed and others are transmitted
Green light is TRANSMITTED (which’s why leaves appear green) and red and blue light is absorbed, so plants growing underneath other plants receive reduced amounts of red light
It’s the reduced ratio of red light to far-red light that elicits a phytochrome response
Phytochrome not only detects light quality, but it regulates…
gene expression
When plants receive a lower ratio of red to far-red light, the phytochrome molecule activates a different set of genes
These genes in turn alter morphological, physiological and biochemical characteristics in plants
scientific method
Observing outside world
Asking a question about a natural phenomenon that interests us
Hypothesising an explanation for the phenomenon
Testing the hypothesis through a correlational or experimental study
Collecting and analyzing data from the experiment
Creating a conclusion from the experimental data
observations
The “hows” and “whys” of nature
hypothesis
A tentative answer to the question stemming from your observations
-one or more factors influence the observed phenomenon
-worded in a way that proposes a relationship between one or more factors and the observed phenomenon
-can never be proved only disproved
Since we can only disprove a hypothesis, we create a tool, the _______ (H0) that when rejected provides support for our hypothesis, which we refer to as the hypothesis (Ha; aka “alternate hypothesis” )
null hypothesis
null hypothesis
Null hypothesis states that the factor you are interested in has no effect on the observed results, while your hypothesis states that it has an effect on the results
-Contrary to hypothesis, null hypothesis proposes NO relationship between the factor being studied and the observed phenomenon and can be seen as the default position when trying to explain the observed phenomenon
-For every hypothesis you make (that something interesting is happening), there will be a corresponding null hypothesis (that nothing interesting is happening)
experimental manipulations
Experimental manipulations use artificial manipulations to investigate the relationship between one factor and another
correlational studies
Correlational studies use natural variation to investigate the relationship between one factor and another
independent variable
The factor being controlled or manipulated by the researcher is the independent variable
dependent variable
The phenomenon is the response or dependent variable (the variable that’s usually being measured and is not controlled by researcher)
control
A control is a reference to which the results of an experimental manipulation can be compared
-E.g. if we want to investigate the effect of smoking on human lung tissue, we need a control group of non-smokers to compare with a treatment group of smokers
-Controls are important to ensure that the conclusions drawn from an experimental manipulation are biologically valid
confounding variables
Confounding variables are factors that the researcher failed to control or eliminate in which can damage the validity of an experiment
controlled variables
Controlled variables are variables held constant in a study
advantages of a correlational study
- Less handling time of organisms
- Systems under study are more likely to be observed in their natural state
-mere act of manipulation can introduce differences among treatments, which can affect our results and conclusions - Represent biologically relevant variation
4.There are situations where experimental manipulation is not practical or ethical
advantages of an experimental manipulation
They are more likely to control for confounding variables
We know the direction of causation
importance of plant-animal interactions
Plants produce almost all energy available in terrestrial ecosystems
Important energy source for other organisms
Animals that feed on plants receive this energy indirectly
Plants provide shelter and provide survival for most animals
Plants can’t be displaced, animals help them with seed dispersal/reproduction
These can lead to adaptations→leads to diversity
positive species interaction
Positive→species benefit from the interaction
negative species interaction
interaction is costly for species
__________ determines the nature of the interaction (if the costs outweigh the benefits, then the interaction has a negative effect on species)
Net effect
competition
When interaction has negative effect on both species →competition
Competition arises when both species require the same resource
Not common between plants and animals (only between animals)
mutualism
Mutualism → interactions in which both species benefit
E.g. ant in tree (ant gets shelter, tree gets more resources), pollination
consumer-resource interaction
positive effect on one and negative effect on the other
Consumer benefits and the resource suffers a cost
Relationship between predator-prey, parasite-host, herbivore-plant
plant herbivore interactions
Organisms feed on foliage, eating entire leaves or portions of them
Only one type of herbivory and different organisms (different feeding modes)
Herbivores can have strong effects on plants
Removal of plant tissue negatively impacts plant’s fitness
-plant feeding reduces amount of resources for photosynthesis, plant growth and production of seeds
-herbivores that consume and kill seeds have a negative effect on plant fitness
-flowers consumed → pollination and reproductive success reduced
-herbivores can also indirectly decrease fitness by transmitting viruses between plants through their mouthparts or saliva
plant resistance
plants can resist herbivores through tolerance/defense
tolerance
Tolerance is a plant’s ability to to reduce the effects of herbivory on fitness
Plants can tolerate herbivory by physiological responses
e.g. move resources from roots to shoots following herbivory in order to stimulate shoot growth and replace lost tissue
defense
Defense is a trait that reduces damage to a plant by herbivores
-3 categories:
Timing of flowering or leaf production
Structural defenses
Chemical defenses
Plant can employ more than one defense against herbivores, and they can combine different types of defenses:
plants can have both structural and chemical defenses
phenology
study of life cycles of plant and animals in relation to seasonal change
-plants can defend themselves from herbivore damage by producing leaves or flowers when herbivores are least abundant
-may also present flowers or leaves simultaneously instead of sequentially
-this could reduce damage by herbivores if herbivores can’t eat as much of the plant tissue in simultaneous presentation as in sequential presentation
trichomes
traps herbivores and prevents them from laying eggs or makes it difficult for them to feed on leaf tissue
constitutive defenses
Defenses costly to make so only produced by plants when needed→ constitutive defenses
induced defenses
produced or increase their levels of expression following damage by a herbivore
