Biology Quiz 3 Prep: Lecture 14,15,16,17

Species Defined By BSC

Species are defined by the biological species concept based on the goal of reproductive isolation among populations. NO GENE FLOW. This means that members of different species cannot interbreed and produce viable, fertile offspring.

Prezygotic Isolation

A mechanism that prevents mating or gene flow between different species, ensuring reproductive isolation before the formation of a zygote. Based on three different concepts: Temporal (time), Habitat (isolated because of different habitats), behavioral, gametic barrier, and mechanical.

Postzygotic isolation

A reproductive barrier that occurs after fertilization, preventing the development of viable, fertile offspring. This includes mechanisms such as hybrid viability, hybrid sterility, and hybrid breakdown.

Problems w/ BSC

Species need to be co-located to demonstrate reproductive barriers. Cannot be tested in fossil specimens, does not apply to asexual organisms, difficult to apply when hybridization is common.

Species Defined by PSC

A concept that defines species based on their evolutionary history and phylogenetic relationships, emphasizing the smallest group of individuals that share a common ancestor.

Monophyly

Groups of taxa that contain all known descendents of a single common ancestor

Problems w/ PSC

Issues arising from defining species based on phylogenetic relationships include difficulties in determining ancestral traits, potential for oversplitting species, and challenges in interpreting incomplete or ambiguous data. Not many good phylogenies.

Species Defined by MSC

A concept that defines species based on morphological characteristics and physical traits, often focusing on observable features rather than genetic or evolutionary relationships.

Problems w/ MSC

Issues related to defining species based on morphological characteristics include subjectivity in trait selection, potential for overlooking genetic diversity, and challenges in accounting for variations within species.

Three stage process of speciation

1. Isolation of populations

2. Divergence between populations

3. Reproductive isolation of populations

Vicariance

A process in which a species' range is split into separate populations due to geographical barriers, leading to speciation.

Isolation of Populations

The separation of groups of organisms, often due to geographical barriers or environmental changes, which prevents interbreeding and allows for evolutionary changes to occur.

Divergence between populations

The process by which two or more populations evolve different traits or characteristics over time, often due to different selective pressures or adaptations to their environments.

Reproductive Isolation

The inability of different species or populations to interbreed and produce viable, fertile offspring, often due to behavioral, temporal, or mechanical barriers.

Extirpation

Loss of a species locally, populations may exist elsewhere.

Extinction

Complete Loss of a species, no individuals anywhere

Background Extinction

The normal rate of extinction occurring in the absence of human influence, typically due to natural processes such as environmental changes.

Mass Extinction

A rapid and widespread decrease in the biodiversity on Earth, typically characterized by the extinction of a large number of species in a relatively short period of geological time.

K-P Extinction

Most Recent extinction, killed off the dinosaurs and other marine species (75%)

Evidence of K-P Extinction

Fossil records indicating a sudden decline in species diversity, including the disappearance of dinosaurs and other organisms, along with iridium layers and geological changes.

Species Area Curves

Used to determine the likelihood of a species going extinct.

Biogeography

global distributions of lineages and diversity

Ways the geographical distribution of a given clade will be determined by:

1. The ancestorial ecological niche of the clade

2. The geographical starting point for dispersal (tectonic history)

3. Limitations to dispersal due to abiotic conditions and other species

4. Opportunities for niche evolution that are afforded to species by the geographic location

5. the amount of time since the origin of the clade, during which Niche evolution and dispersal could occur

Ancestral niche of the clade

Niche: set of physical and environmental conditions a species requires and interactions it has w/ other species.

Ex: cacti: Arid environments, limited to Americas, Seed dispersal by birds, Limited by freezing temps

Geographical starting point for dispersal

History of earth: pangea, gondwanaland, land bridges

Ex: ostriches, depending on location is when you lost flight

Limitations to dispersal imposed by abiotic conditions and species

Dispersal: movement of individuals from where they were born to where they live

Locomotion: flying versus walking, wind dispersed, water column

Ex: Pleitocene Glaciation

• Change in climate, climate zones shift toward equator, species w/ low dispersal capabilities had to adapt to new climatic regions

Opportunities for niche evolution that are afforded to species by the geographic location

species unlikely to adapt to ecological conditions that they were never exposed to

Ex: salamander diversity in SE US, ancestors lived in higher elevations

The Amount of time since the origin of the clade, during which niche evolution and dispersal could occur

Why are there lots of species in the Tropics: Tropics occurred over large extents until 30 MYA, more clades originated here therefore.

Biological Map

atom→molecule→organelle→cell→tissue→organ→organ system→organism→population→community→ecosystem→biosphere

3 Properties of Populations

1. Size

2. Distribution

3. Density

BIDE

Determines Population size (Birth, immigration, death, emigration)

Why calculate population sizes:

For endangered species count, reproductive success

Ways to quantify Population

1. Linear Model

2. Exponential Model

3. Logistic Model

Linear Model

Population increases steadily with no per capita rate.

Ex: N₀ = 10

2 rabbits born per year

Limitations to Linear Model

Doesn’t factor in environmental concerns, no loss, birth rate isn’t a function of pop size

Exponential Model

Population grows steadily at a rate.

Ex: N=10

2 Rabbits born/rabbit

0.5 deaths/rabbit

Per capita growth rate: 1.5 (2-0.5)

Causes exponential curve

Point of Crisis

Point of exponential curve where the limiting resource affects population growth. “Law of minimum phenomena”

Logistic Model

Same stats as exponential model

Adds carrying capacity (K)

Grows steadily than plateaus

Assumptions: Steady Environment

Best model

Carrying capacity

Max number of individuals in a population

When N is Not close to K, what happens

K-N is LARGE, population is growing faster

When K is close to N

K-N is small, population is growing slowly

When N=K

Growing stops

When N>K

Limiting resources, growing shrinks

Life Tables

Lets you access births/deaths over life/age stages of the population

Uses cohort classes

Assumptions: no immigration or emigration

Cohort Classes

Groups of individuals of the same age

Net productive rate

R₀ = average birth rates per year per females

R₀ > 1

INCREASING population

R0 <1

Decreasing Population

R0=1

Stable Population