Evolution by Natural Selection
Natural Selection
Adaptation
Selection/survival
Reproduction #
Population change over time
organisms that are best adapted survive
VASRP
natural selection is dependent on...
Heritable traits
advantageous
defined as
differential reproduction of inheritable variants
survival of the "fittest"
process, which random evolutionary change is selected by nature
eliminates non-favourable traits organisms possess
sub branches of natural selection
sexual selection
organisms that are best adapted survive
one of the several key concepts of evolution
consistent, orderly, non-random way
pressure that causes organisms to change
physically
behavioural
constant influence of evolution within a population
environment
best characteristics survive
present-day organisms developed from past organisms
within a population
traits are inherited
inherited from parents
traits can be beneficial or non-beneficial
a difference in organisms
physical
behavioural
E.g. Body size or hair colour
E.g. attracting mates
avoiding predation
Exposure to preadators
Stabilizing selection #
majority of population is "normal"
some "outliers"
not common
common within the population
directional selection #
Trait is common
caused by trait being more favourable
diversifying selection #
both traits are desirable
50 percent from mother and 50% from father
Adaptations are developed
adaptations help organisms survive
certain adaptations are more advantageous over others
favourable traits increase chance of survival
Non-favourable traits decrease chance of survival
traits are favoured in certain environments and resource
organisms that struggle
allow for adaptation
have little use to organisms/ population with small numbers
Environmental pressures
change in environmet
changing resources
increased competition
predation
Predator- prey
variation is developed to avoid predation
trait give higher chance of surviving
mutation
occurs at low rate
random genetic drift
from one generation to another
process of pure chance
Survival of the "fittest"
struggle for resources #
individuals best suited for their environment
more likely to survive
more likely to reproduce
Selection occurs because of differences
fertility rates
rate of development
mating success
other aspects of the life cycle
encourage faster development of adaptations
traits may suit one environment, not another
organisms that make live to reproduce
traits that allow for survival
increase in future generation
which genes individuals carry
increase competition
genetic drift
occurs in all population
frequencies of a population change over generation
founder effect
bottle neck effect
small group of population
split from main population
establish new colony
natural disaster
dramatic reduction of population
E.g. earthquake, flood, fire
leave small and random assortment of survivors
isolated from original population
doesn't represent full diversity of original populations
similar to bottleneck
different mechanism
colonization rather than catastrophe)
does not depend on beneficial or harmful effects
surviving population reproduce
heritable traits
traits that can be inherited by offspring
Less favourable genes
less likely to be inherited by offsping
mutation may occur #
favourable genes
likely to be inherited by offspring
likely to continue passing the gene
measure of reproductive efficiency of traits
may be advantageous
relative fitness
relative probability of inheritable traits inheriability
not advantageous
filtered out by natural selection
Organisms reproduce more than environment can sustain #
example
rock lobsters release 300,000 eggs
only 30 eggs survive to reproduce
characteristics best suited will survive, reproduce and pass their characteristics to offspring
over time
generations of populations characteristic change
favourable traits become common
less favourable traits
lead to improvement
in survival
in continuation of species
likely to die out
likely to be less common
E.g. Large size is better than small
population will become adapted to its environment
SCIENCE ESSENTIALS 10 FOR NSW S Stage 5
5
4
competition for survival
fittest survive #
3
2
1
6
7