Study Guides (390,000)
US (220,000)
UC-Irvine (3,000)
BIO SCI (300)

BIO SCI 94 Midterm: Bio94 Midterm1 Key Ideas

Biological Sciences
Course Code
Nancy Aguilar- Roca
Study Guide

of 8
Chapter 1: Biology and the Tree of Life
●Natural Selection is the process by which individuals vary in characteristics
that are heritable and individuals with certain heritable traits tend to produce
more surviving offspring than do individuals without those traits, leading to a
change in the genetic makeup of a population.
●Population is a group of individuals of the same species living in the same area
at the same time.
●Evolution occurs in populations when heritable variation leads to differential
success in reproduction (descent with modification).
●Fitness means the ability of an individual to produce viable offspring.
Individuals with high fitness produce many surviving offsprings.
●Adaptation is a trait that increases the fitness of an individual in a particular
●Cell Theory and Theory of Evolution state that the cell is the fundamental unit in
all organisms and all species are related by common ancestry and have
changed over time because of natural selection.
●If the theory of evolution is correct then the rRNA sequences should be very
similar in closely related orgasims, but less similar in organisms that are less
closely related. Species that are part of the same evolutionary lineage like
plants should share certain changes in rRNA that no other species have.
●Phylogeny is the evolutionary history of a group of organisms.
●Phylogenetic trees show the evolutionary relationships between species. Node
is the common ancestor of all living organisms.
●Three Fundamental Lineages: Bacteria, Archaea and the Eukarya. Bacteria and
Archaea are referred to as prokaryotes (lack a nucleus) and are unicellular.
Eukarya are eukaryotes (have a nucleus) and are mostly multicellular. These
are the three domains of life. Phylum refers to the major lineages within each
●Taxonomy is the effort to name and classify organisms. Any named group is
called a taxon.
●Genus is the first part of the scientific latin name and is made up of a closely
related group of species (ex. Homo for humans). Species is the second term
that identifies the species (ex. Sapiens). (ex. 
Homo sapiens).
find more resources at
find more resources at
Chapter 25: Evolution by Natural Selection
●Evolution is descent with modification meaning that species that lived in the past
are the ancestors of the species existing today, and that species change
through time. Species are related by common ancestry.
●Fossil is any trace of organisms that lived in the past and this was used to
prove that change occurred through time. Younger layers of rock are
deposited on top of older layers. Earth is about 4.6 billion years old and rock
formed 3.4-3.8 billion years ago.
●Extinct species are species that no longer exist. Fossil records suggest that
over 99% of all species that ever lived have gone extinct. Extinct forms and
living (extant) forms are related and represent ancestors and descendants.
●Transitional feature is a trait in a fossil species that is intermediate between
those of ancestral (older) and derived (younger) species.
●Vestigial trait is a reduced or incompletely developed structure that has no
function or reduced function, but is clearly similar to functioning organs or
structures in closely-related species, this proves that characteristics of
species change over time. They don't increase the fitness and are not adaptive.
●Homology is a similarity that exists in species because they inherited the trait
from a common ancestor. Most fundamental, genetic homologies (occurs in DNA
and RNA nucleotides sequences, or amino acid sequences) cause the
developmental homologies observed in embryos, which then lead to the
structural homologies (similarities in adult morphology, form/structure, but
with different functions) recognized in adult. DNA is homologous in all organisms.
●Internal consistency is the observation that data from independent source(
relative dating, absolute dating and phylogenies) agree in supporting
predictions made by a theory.
●Artificial selection is the process by manipulating the composition of the
●The outcome of evolution by natural selection is a change in allelic frequencies
in a population over time.
●Evolution by natural selection occurs when heritable variation leads to
differential reproductive success.
find more resources at
find more resources at
●Natural selection acts on individuals because individuals experience
differential reproductive success. But only populations evolve. Allele
frequencies change in populations, not in individuals.
●Polygenic traits like body size, beak size have many genes that influence their
one trait. Because many genes are involved, it can be difficult for researchers
to know which alleles are changing in frequency.
●During natural selection, individuals do not change-only the population does.
Natural selection acts on the individuals, but the evolutionary change occurred
in the characteristics of the population.
●Darwin realized that individuals do not change when they are selected; they
simply produce more or less offsprings.
●Acclimatization is a change in an individual's phenotype that occurs in
response to a natural environmental condition. These changes are not passed
on to offspring because no alleles were changed, so it doesn't cause evolution.
●Mutations just happen. Adaptations do not occur because organism want or
need them.
●Adaptations are limited by genetic correlation, lack of genetic variation, fitness
trade-off and history.
●Genetic correlation occurs because of pleiotropy, in which a single allele is
affected by multiple traits
●Fitness trade-off is a compromise between traits, in terms of how those traits
perform in the environment.
●All traits have evolved from previously existing traits.
find more resources at
find more resources at