Unit 2 - Chapter 1 - Adaptation & Natural Selection Flashcards
What is meant by an adaptation?
Something that confers and advantage to survival.
“refers to the process or trait through which organisms or the populations in a habitat become more suited or a better fit to their environment.”
Evolution shapes adaptations through NATURAL SELECTION.
what is NATURAL SELECTION?
Organisms with particular heritable character have higher reproductive success than other individuals in a particular environment.
It is selective pressures – the environment imposes selection pressures on the species and the allele frequencies of the genotype changes over generations. “While it may make sense that natural selection would act on the genotype, an organism’s genetic make-up, the action actually occurs on the phenotype, an organism’s physical traits.”(online).
Organisms are adapted to interact with their environment.
Is it synonymous with evolution? NO. Natural selection is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time (Source: Natural History, UK)
What is the ‘fitness’ of the species?
the proportionate contribution made by an individual to future generations relative to other individuals in the same population.
In a particular environment with a given set of environmental conditions, individuals with characteristics that confer higher rates of survival and reproduction have more offspring. Those characteristics are more frequent in the next generation.
Selection for individuals that maximize their lifetime reproduction success(which is measured by # of offspring)
Who will a species be in the most DIRECT competition with?
Species that live in the same area and use similar resources!
What are some examples of adaptation that have evolved to enable organisms to overcome specific challenges?
Examples of adaptations are fur, feather and fat (to help animals keep warm in cold habitats), long legs (to help animals escape from their predators) or camouflage (to help animals hide from their predators).
ex: beak size of the finches on Daphne Major varies – the variation in beak depth is HERITABLE
For the ground finches on Daphne Major:
- beak size & FOOD: birds with smaller beaks ate softer seeds. birds with longer beaks ate the harder seeds.
- During the drought, there were more hard seeds. So the birds with longer beaks would have a better survivability chance.
What is phenotypic variation?
Will the same phenotype be advantageous in all environments?
NO. Depends on environment. Selective pressures will be different in each environment. Food & climate differences.
Phenotypic Plasticity?
Developmental Plasticity?
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```the ability of one genotype to give rise to different phenotypes under different environments. Different genes are expressed more than other genes. Norm of reaction is the set of phenotypes expressed by a single genotype across a range of environmental conditions.
Results from:
1. developmental plasticity
2. acclimation
environmental conditions can vary
How can it increase fitness? more offspring, better lifetime reproductive success (LRS)
ex: the body temperature of many insects is affected during development due to a warmer temperature
Developmental plasticity refers to the evolved and ubiquitous ability to adjust phenotypic development in response to environmental cues experienced in the more plastic early stages of development (Bateson et al., 2004). It is the basis by which multiple phenotypes may be generated from a single genotype.
What is meant by ‘acclimation’?
phenotypic plasticity in response to current environmental conditions that is reversible (?)
Advantages : better survivability, less stress on the organism to live daily life.
It’s not evolutionary change: “Adaptation is a gradual, permanent change that is evolutionary important for a species’ survival and continuity, Acclimatization is a quick, temporary change that can be reversed once the previous conditions are met. Note: Acclimatization has no long-term effect on the genetic mechanisms of the acclimatized organism.”
What is a ‘cline’?
a measurable change in a single, phenotypic character of one species across it’s geographical range
A cline usually follows an environmental gradient that also varies over the geographic region.
Continuous variation in the character results from gene flow between populations along the gradient.
Step clines indicate an abrupt change in environment and in the phenotype and genotype of the organism. These variants in different populations of a species are called ecotypes (a population adapted to its unique environmental conditions)
What kind of experiment is done to study these clines?
‘Common Garden Experiment’
What is the ‘Common Garden Experiment’?
Common garden experiments are indoor or outdoor plantings of species or populations collected from multiple distinct geographic locations, grown together under shared conditions. These experiments examine a range of questions for theory and application using a variety of methods for analysis
What if the plants are genetically distinct?
What if the plants are due to phenotypic plasticity?
One way to quantify phenotypic plasticity is to use analysis of variance (ANOVA). The idea behind ANOVA is to take a variety of genotypes and a variety of environments and assess the resulting phenotype for each genotype-environment pair.
What is the difference between phenotypic plasticity and genetic adaptation?
Local adaptation involves genetic differentiation specific to each environment, whereas phenotypic plasticity allows single genotypes to express different phenotypes under diverse environmental conditions.
