Evolution Flashcards
What is biological evolution?
A genetic change in a population over generations
What is fitness?
How well an individual is able to reproduce within its environment
What are the components of fitness?
Survival + reproductive success
What is sexual selection?
Selection of traits that give an individual an advantage in attracting mates, even if these traits are neutral or harmful for survival
What are they types of sexual selection?
Intrasexual selection and intersexual selection
What are selection pressures?
External agents which affect an individual’s ability to survive and reproduce within an environment
What are biotic selection pressures?
Living organisms within the same ecosystem that interact with the affected individual and affect fitness
What are abiotic selection pressures?
Non-living factors within an individual’s environment that affects fitness
What are the characteristics of a selection pressure?
- act on all stages of the life cycle
- may act for many generations
- act on the phenotype
What is essential for natural selection to occur?
- system of reproduction
- inherited variation
- differential reproductive success
- changing environment
- selection pressures
What were Darwin’s observations?
- Organisms have great potential fertility which enables populations to grow exponentially
- Natural populations normally do not increase exponentially but remain fairly constant in size
- Natural resources are limited
- Variation occurs among organisms within a population
- Variation is heritable (offspring look like their parents)
What were Darwin’s inferences?
- A struggle for existence occurs among organisms within populations
- Individuals show differential survival and reproduction, favouring advantageous traits (natural selection)
- Natural selection, acting over many generations gradually produces new adaptions and new species
When may vestigial organs arise?
When a species changes its lifestyle
What are species found in the fossil record known as?
Chronospecies (paleospecies)
What is punctuated equilibrium?
Evolution consisting of period of no or very little change followed by relatively large changes in a relatively short space of time
What is an example of punctuated equilibrium?
Horseshoe crabs have existed unchanged for approximately 250 million years
What were key concepts when Darwin was developing his ideas about evolution?
Hutton and Lyde’s ideas that the earth was old and continually changing
How did Darwin describe evolution?
“Descent with modification”
What book presented a mechanism for natural selection?
The Origin of Species
What is macroevolution?
The descent of different species from a common anscestor over many generations
What is micro evolution?
Changes in gene frequency in a population from one generation to the next
The genetic code is an example of a ________
Homology
What are some examples of biotic selection pressures?
- predation
- competition
- disease
What are some examples of abiotic selection pressures?
- climate
- topography
- habitat
What are the 3 types of natural selection?
Stabilising
Directional
Disruptive
What is stabilising selection?
Selects against extreme phenotypes
What is directional selection?
Selects at one end of the phenotype so that the phenotypic character shifts in one direction
What is disruptive selection?
Selects against average phenotypes
What is an example of stabilising selection?
Birthweight and infant mortality
Who is the selective pressure in artificial selection?
Humans, uses the process of natural selection
What is intersexual selection?
When a female chooses a male mating partner based on a particular trait
What is intrasexual selection?
When members of the same sex within a population compete with each other in order to gain mating opportunities
What is gradualism?
Evolution that happens gradually and over a long period of time
What is anagenesis?
Evolution within a single lineage
What is cladogenesis?
Branching evolution, where two new species evolve from a common ancestor
How do fossils and where fossils are found provide evidence for evolution?
- fossils in deeper layers are older than those above and their position within these rocks gives them a chronological age relative to older or younger fossils
- fossils of more complex organisms are found in recent rock formations
- the fossils in older layers will be more simple and primitive
- the fossils found in newer layers are more diverse and samples than those found on older layers
What is an intermediate form?
An organism intermediate of two species
What is the bird intermediate form?
Archaeopteryx
What type of evolution is an intermediate form an example of?
Cladogenesis
What is the fossil record evidence for?
- perpetual change
- common ancestry
- intermediate forms
- cladogenesis
- anagenesis
- evolutionary failure
- evolutionary stability
What is comparative anatomy?
The study of similarities and differences in the anatomy of different species
What are analogies the result of?
Convergent evolution
What are homologous traits?
Traits that share an underlying similarity due to common ancestry and divergent evolution
What is adaptive radiation?
Process whereby rapid cladogenesis is seen, if new niches become available to a species
What are analogous structures?
Traits that have the same appearance, structure or function but have evolved separately due to convergent evolution
What is a vestigial feature?
Features that become reduced because they no longer perform a function
What do features become vestigial?
Structures that are large but have no function wastes metabolic energy to maintain
How do analogous features evolve?
Independently through similar environmental selection pressures
What is convergent evolution?
Seperate lineages that were quite different become similar because of similar lifestyles
What are homoplastic features?
Features that are similar in appearance, may or may not be homologous or analogous
What are atavistic structures?
When an ancestral trait reappears in a species after being lost through evolutionary change
What is an example of an atavistic feature?
A horse being born with additional toes
In what ways is artificial selection evidence for evolution?
- variation in populations
- descent with modification
- rapid change
- mechanism of evolution
What is a phylogenetic constraint?
Refers to the limitations of future evolutionary pathways that have been imposed by previous adaptions
What is an example of a phylogenetic constraint?
Terrestrial vertebrates have a body plan that consists of four limbs
What is comparative embryology?
The comparison of embryo development across species
In what ways may a peacocks tail reduce survival?
- it is very large and unwieldy so it requires more energy to drag around, energy that could be better used for just staying alive
- it is very visible so males are potentially more visible to predators and less able to escape quickly with such a bulky tail
- it is very costly to grow, again using energy that could be used elsewhere
How can a peacocks tail can actually result in an increase in fitness even though the survival of the individual may be compromised?
- fitness consists of survival and fertility
- if the increase in fertility through the ability to attract multiple mates outweighs the decrease in survival, then overall fitness is increased
In what ways might a peacocks tail potentially increase that individual’s reproductive success?
- it acts as a sensory cue imparting information about a male’s mating value (in terms of the quality of his genes) to peahens who then mate preferentially with the male with the best tail
- the male with the best tail ends up with more partners compared to other males in the population, which can result in more offspring
Why are analogies present?
Because two species share a common lifestyle
What is fitness?
The ability for an individual to survive and reproduce so that it’s genes are passed onto the next generation
What is punctuated equilibrium?
Rapid evolution followed by long periods of little or no change
