Biology Cycle 7 Flashcards
What is sexual selection?
–> type of natural selection
–> usually male competition for access to females and by female’s choice of mate
What is intersexual selection?
selection based on interactions between males and females
–> ornate structures/behaviour/display/calls
that are associated with attractiveness or health/fitness
What is intrasexual selection?
selection based on interactions of the same sex
–> competing intimidate, injure, or kill rival males
–> males monopolize access to females
–> control of females/resources important to females (food/territory)
What does intersexual selection give rise to? Why?
SEXUAL DIMORPHISM – differences in size/appearance of males or females
–> selection drives males to evolve differently from female to gain ornamentation
How does sexual selection cause changes in populations?
Alike to DIRECTIONAL selection; pushes phenotypes to one (very) extreme which might not be necessary for any purpose other than intersexual selection
How does sexual asymmetry impact mating?
eggs are more energectically expensive than sperm
What are the limits of fitness for fitness in males and females
What do the limits indicate for mating?
Females – production of eggs
Males – number of females an individual can mate with
–> females must be more selective with mates
What do the features of males that females select from imply?
- ability to obtain resources/food/territory
- produce healthy offspring
- protection of offspring
- attractive individuals: good alleles ensure attractive offspring (offspring have high fitness/ chance of survival)
What is reproduction?
means of passing on an individuals’s genes to a new generation
What is the difference between asexual and sexual reproduction?
asexual: SINGLE individual creates offspring (no genetic input from another individual)
–> genetically identical offspring
sexual: union of egg/female and sperm/male to create a fertilized egg - zygote -
–> increases genetic diversity
What is reproductive strategy? Which type of reproduction is the best strategy?
a set of behaviours that lead to reproductives success
–> either are advantageous depending on the environment
What are the advantages of asexual reproduction?
- in uniform, stable, unchanging environments or sessile (immobile) animals
- no need to produce gametes
- no need to find a mate
How does asexual reproduction occur in animals?
FISSION, BUDDING, PARTHENOGENESIS
Why are offspring from parthenogenesis not identical?
Egg of offspring is produced from meiosis in the female parent if the egg goes from haploid to diploid
What are the disadvantages of sexual reproduction?
- cost of energy/raw materials/time-consuming for producing a gamete and find a mate
- possibility for infection/disease
- conflict for food and shelter
- predation exposure
Can organisms reproduce sexually and asexually?
Yes; depending on environment
What sexual dimorphism? What is sexual monomorphism?
dimorphism: sexes look different
monomorphism: sexes look the same
What is the difference between natural and sexual selection?
natural - traits that increase survival and fitness are favoured and are passed onto offspring –> these traits increase in future generations
sexual - traits that increase mating success and individual fitness are favoured
How does directional selection in natural and sexual selection compare?
NATURAL: shift of alleles towards favourable alleles from non favourable alleles
SEXUAL: shift from female phenotypes to male phenotype resulting in dimorphism
How might sexual selection reduce survival?
favourable traits might be exaggerated making survival difficult (ex. birds with very long tails have difficulty flying)
Which sex selects their mate?
sex that invests more in parental care (usually females) to ensure quality of offspring since they have fewer contributions to the next generation
Which traits are favourable in intersexual selection? Which traits are favourable in intrasexual selection?
inter - traits that are more attractive (ornamental)
intra - traits that are stronger
How does intrasexual selection relate to intersexual selection?
–> males compete through performances of calls/dances/behaviours/structures
What are examples of sperm competition?
INTRASEXUAL
1. swimming speed - fastest sperm fertilizes egg
2. scrapers - scrape out sperm deposited by other males
3. mating plugs - after mating, males leave a plug to prevent other males from mating
How can phenotypes be used to reduce competition?
mate quickly before dominant male noticing by impersonating females to access guarded females (ex. cuttlefish male colouring)
How can phenotypes be used to reduce competition?
mate quickly before dominant male noticing by impersonating females to access guarded females (ex. cuttlefish male colouring)
How does reproductive success of males and females compare?
average fitness is the same for each sex
How does reproductive success compare between females?
generally equal reproductive success
How does reproductive success compare between males?
higher POTENTIAL fitness for any one individual, lowest quality has the lowest reproductive success - individual fitness can vary widely
How does parental care impact sexual dimorphism?
when one sex provides more parental care, they are unavailable for mating with others
–> other sex must compete more
–> under stronger sexual selection
–> drives evolution towards favourable traits
**in males and females
What is the result of biparental care?
males removed from seeking additional mating opportunities so there is less dimorphism
–> both sexes compete and both sexes choose
–> sexual selection acts on both sexes
What is sex?
exchange of genetic material
What is the relationship between sex and reproduction?
it can either be in the same process or in different processes
What occurs when sex is the same process as reproduction?
sexual reproduction
-> gametes fuse to generate new combinations of alleles in the offspring
Which species undergo sexual reproduction?
animals, plants and other eukaryotes
Why do offspring have a new combination of alleles unlike the parent alleles in sexual reproduction?
sex (genetic exchange) and recombination
What occurs when sex is separate from reproduction?
sex is only genetic exchange from another organism (which can be distantly related) or their environment and reproduction is ASEXUAL
Which species undergo asexual reproduction?
bacteria, archaea (prokaryotes)
How does sex occur in bacteria and archaea?
CONJUGATION - transfer of plasmid
TRANSFORMATION - DNA from environment (ex. dead cells)
TRANSDUCTION - DNA moved around by viruses, transposons, mobile elements
What are the ways in which organisms reproduce?
obligately asexual, facultatively sexual, obligately sexual
How do obligately asexual organisms reproduce?
ONLY asexual reproduction (cell division) and sex is just genetic exchange
How do facultatively sexual organisms reproduce?
sexually or asexually
What are examples of unicellular and multicellular organisms that are facultatively sexual?
EUKARYOTES
uni. - protists
multi. - plants
How do obligately sexual organisms reproduce?
ONLY sexual reproduction
How do the resulting offspring of asexually reproducing organisms compare with the parent?
genetically identical - CLONES unless sex, recombination or mutation occurs prior to division
How does asexual reproduction compare between prokaryotes and unicellular eukaryotes?
bacteria & archaea by binary fission
unicellular eukaryotes (ex. protists, yeasts) by mitosis
How does asexual reproduction occur in plants?
new individuals grow from a tuber (potato) or from a runner (strawberry) that are genetically identical
What is budding?
new individual grows and develops while attached to parent
What is fragmentation?
pieces separate from a parents body and regenerate into new individuals
What is parthenogenesis?
females produce offspring without sperm fertilizing their egg so their is no sex
What is the ploidy of offspring produced by parthenogenesis?
unfertilized egg remains diploid during gamete formation so there is no meiosis
–> offspring are clones
or
DNA in haploid egg replicates and becomes diploid
–> offspring are not clones
What is the difference between sexual reproduction in animals and plants vs fungi and protists?
ANIMALS & PLANTS:
- fusion of different gametes produced by different sexes
FUNGI & PROTISTS:
- two or more mating types
- cells fuse or nuclei exchanges and nuclei fuse
What are dioecious species?
individuals of separate sexes (most animals, some plants)
What are monoecious species?
individual plants are both sexes and have both reproductive structures (most plants are monoecious)
What are hermaphrodites?
individual animals are both sexes and have both reproductive structures (some animals)
How do monoecious plants display reproductive tissue of both sexes?
ex. male and female in the same flower
or
ex. separate male and female cones on the same tree
What are the two types of hermaphrodites?
simultaneous or sequential
What are simultaneous hermaphrodites characterized by?
male and female reproductive structures at the same time in animals (ex. worm individuals have ovaries and testes)
What are sequential hermaphrodites characterized by? What are the two types?
starts as one sex and develops into another (protandry - male first & protogyny - female first)
What species is commonly sequential hermaphrodites? Why does this occur?
fish –> if a dominant female dies or size advantage for reproductive/mating success
When does protandry occur?
if a dominant female dies or if males have more reproductive success when smaller in size and the reproductive success increases when they become females
When does protogyny occur?
when females have more reproductive success when smaller and develop into males increase reproductive success
How did sex/reproduction occur 4 billion years ago?
–> life evolved - LUCA reproduced asexually but also likely had sex (exchange genes)
How did sex/reproduction occur 2 billion years ago?
–> eukaryotes evolved - most eukaryotes can reproduce sexually since meiosis evolved for the fusion of gametes
How does sex/reproduction occur today (compared to 2-4 billion years ago)?
asexual - bacteria, archaea, and some eukaryotes have separate sex
sexual - most eukaryotes can produce along with sex and most ANIMALS MUST reproduce sexually
What is the result of the rarity of asexual animal reproduction?
they are prone in extinction
How is genetic information lost in sexual reproduction?
only half of an individual genetic information is passed on to offspring so for ever generation, sexual individuals pass on 2x less of their genetic material = two-fold cost of sex
Why is sexual reproduction inefficient compared to asexual reproduction?
only females “grow”/contribute new offspring so producing a male reduces reproductive output, so asexual population grow much faster
What are the evolutionary benefits of sex in terms of variation?
greater population variation leads to potentially greater adaptability since there is an increased probability of have some offspring surviving/having favourable phenotypes
What are the evolutionary benefits of sex in terms of allele combination?
sex (genetic exchange)/recombination can bring beneficial alleles together to create the highest fitness (more fit than parents) more quickly
–>more efficiently remove bad allele combinations through selection
What is clonal interference?
asexual reproduction preventing combinations of “good” mutation
What are the evolutionary deficits of asexual reproduction?
beneficial variants cannot be combined unless there is sex multiple times which is slower to highest fitness than sexual reproduction
Why is sex important in macroevolution?
- variation in phenotypes that are not identical to parents
- occurs more frequently in related individuals (same species) so there is a shared gene pool
- no sex = speciation (creation of new species)
