Bio Flashcards

Comparative Embryology 

Closely related organisms go through similar

stages in their embryonic development.

Comparative Anatomy

Study of Anatomical structures and 

Evolutionary relationships.

Comparative Anatomy

Study of Anatomical structures and 

Evolutionary relationships.

 

• Homologous structures

•  Analogous structures

•  Vestigial structures

Homologous structures:

different function

same structure (morphologically similar)

same common ancestor

Analogous structures: 

same action/function,

different structure,       

different ancestor

Vestigial structures:

remnants of structures that served important functions in the organism’s ancestors

Fossil Record

The progression of forms observed in the fossil record is consistent with other inferences about the major branches of descent in the tree of life.

Molecular Biology

Scientists examine the nucleotide of DNA and amino acid sequences of proteins from different species. Closely related species 

share higher percentages of DNA & amino acid sequences than species that are distantly related.

Endosymbiosis

Scientists believe mitochondria and chloroplasts were originally independent prokaryotic bacteria. They entered into a symbiotic relationship with a large, ancestral cell. 

Endosymbiont Theory

• Replication by binary fission

• Single, circular DNA

• Ribosomes to make proteins

• Enzymes similar to living prokaryotes

• Two membranes around organelle

Biogeography

The use of geography to describe the distribution of species. 

DIVERGENT EVOLUTION (aka Adaptive Radiation)

New species evolve from a common ancestor. 

CONVERGENT EVOLUTION

A kind of evolution where organism evolve structures that have similar (analogous) structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated

COEVOLUTION

Influence of closely associated species on each other in their evolution

PUNCTUATED EQUILIBRIUM

A theory that describes an evolutionary change happening rapidly and in brief geological events in between the long periods of stasis (or equilibrium)

GRADUALISM

A theory stating that evolutionary change happens slowly, steadily and gradually in an attempt of the species to continue to adapt to new challenges

Evolution

A process of gradual change that takes place over many generations, during which species of animals, plants, or insects slowly change some of their physical characteristics

Natural Selection

The process whereby organisms better adapted to their environment tend to survive and reproduce more offspring. 

Fitness

How well a species is able to Survive & reproduce in its environment

How does natural selection play a role in the survival of an organism?

1.  Variation: differences within a population

2.  Overproduction: All species tend to produce more offspring than they can support

3.  Competition: Competing for limited  resources

4.  The “fittest” will survive
5.  Nature (the environment) will determine which organism is the fittest to Survive

Artificial Selection

The intentional breeding for certain trait or combinations of traits, over others… this can lead to speciation. (Human induced)

STABILIZING SELECTION

Natural selection favors the average for population selected. Decreases genetic diversity and extremes of the trait aren’t as well suited

DIRECTIONAL SELECTION

Natural selection favors one extreme of the population for that trait (Ex. Neck of Giraffe)

DISRUPTIVE SELECTION

Natural selection favors both extremes selected

• Causes species to diverge

• Occurs when two different types of resources in one area 

• Results in specialization for each branched group

• May lead to formation of new species

Examples:

• Darwin’s Finches (different beak sizes)

Population 

A group of organisms that interbreed

Mutations

Mutations are heritable changes to the genotype of an organism that occur randomly and spontaneously within a population

Mutations can affect allele frequency in a population by  

1.  Adding new alleles for a trait

2. Changing the amount of each allele present

Gene Flow (Migration)

Movement into and out of a population can change the allele frequency in  a population’s gene pool, causing gene flow

Genetic Drift

Random changes in allele frequency due to population size

*In smaller populations the allele frequency can change more rapidly than in larger populations

Founder Effect

occurs when a few individuals from a larger population colonize a new area.

Bottleneck effect

occurs when a significant percentage of a population or species is killed or prevented from reproducing.

Non-Random Mating

Having a limited number of individuals can also impact mating

mating can influence allele frequencies because:

• Mates can be limited by geography

• Mates can be chosen for their traits

• Mates can be more closely related to one another

Natural Selection

Natural selection is process by which individual which are more fit for the environment survive and reproduce

Sexual Selection

The competition for mates within a population causing differences to occur in the allele frequencies of the 2 genders. Mates tend to be chosen for their phenotypes and females tend to choose the males

Species

a group of natural populations that are interbreeding or that could interbreed, and that are reproductively isolated from other such groups.

Hybrids

Individuals of different species interbreed and produce offspring called hybrids. 

Reproductive Isolation

The inability of individuals from two populations to produce fertile offspring with each other.

Prezygotic barriers

ake it impossible for individuals to mate with each other or, if they can mate, make it impossible for the male’s reproductive cell to fertilize the female’s reproductive cell

Habitat / Geographic Isolation

Two species living in different habitats, like water and land—even in the same geographic area—are not likely to mate.

Behavioral Isolation

Special mate-attracting signals and behaviors are often exclusive to a species, so even closely related species that do not display such signals are incompatible.

Temporal Isolation

Species that breed during different time periods cannot mate, even if they are very closely related.

Mechanical Isolation

Even when attempted, mating may be anatomically impossible.

Gametic Isolation

Gametes of different species may not be able to fuse to form a zygote, due to either chemical incompatibility or hostile female reproductive tracts.

Postzygotic barriers

Occur after fertilization and generally prevent the production of fertile offspring from individuals of two different species. 

reduced hybrid viability

Hybrid zygotes fail to develop or fail to reach sexual maturity.

Reduced hybrid fertility

Hybrid fails to produce functional gametes

Hybrid breakdown

Offspring of hybrids have reduces viability or fertility