Week 2 Day 3 Origin of Species and Macroevolution

A group of organisms that maintains a distinctive set of attributes in nature.

What is a species?

Mechanisms that promote the formation of new species.

Define speciation.

Evolutionary changes that create new species and groups of species over long periods.

What does macroevolution refer to?

As many as 8.7 million species.

How many species of plants and animals are estimated to exist?

About 1.2 million species, mostly insects.

How many species have been identified so far?

When two or more groups within the same

species display one or more traits that are

somewhat different but not enough to

warrant their placement into different

species Ex. Bengal tiger vs. amur tiger

What is a subspecies?

List some common characteristics used to identify species. (5)

1. Morphological traits,

2. ability to interbreed,

3. molecular features,

4. ecological factors,

5. evolutionary relationships.

A mechanism that prevents one species from successfully interbreeding with other species.

What is reproductive isolation?

Who proposed the concept of reproductive isolation?

The concept was proposed by Dobzhansky in the 1920s.

Mechanisms that prevent the formation of a zygote.

What are prezygotic isolating mechanisms?

Mechanisms that block the development of a viable and fertile individual after fertilization.

What are postzygotic isolating mechanisms?

Give examples of a prezygotic isolating mechanism.

Habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation.

When an egg of one species is fertilized by a sperm from another species, but the fertilized egg cannot develop past early embryonic stages.

What is hybrid inviability?

An interspecies hybrid that is viable but sterile.

What is hybrid sterility?

Speciation that occurs due to geographical isolation of populations.

Define allopatric speciation.

Speciation that occurs without geographical isolation, often through abrupt genetic changes.

Define sympatric speciation.

When a small population moves to a new location that is geographically separated, leading to genetic differences.

What is the founder effect?

The rapid evolution of diversely adapted species from a common ancestor.

What is adaptive radiation?

Each new species evolves continuously over long spans of time.

What does gradualism suggest about the pace of speciation?

A theory suggesting that evolution occurs in rapid bursts followed by long periods of stability.

What is punctuated equilibrium?

A field that compares the development of different organisms to understand evolutionary relationships.

What is evolutionary developmental biology (evo-devo)?

What role do genes play in development? (4 roles)

They influence cell division, migration, differentiation, and death, creating specific body forms and functions.

Each species occupies a unique ecological niche, influencing its habitat and environment.

What is the ecological species concept?

Each species is a population of an independently evolving lineage, descended from specific ancestors.

What is the general lineage concept?

A species is a group of individuals that can interbreed and produce viable, fertile offspring.

What is the biological species concept?

Prezygotic and postzygotic isolating mechanisms.

What are the two categories of reproductive isolating mechanisms?

Mating can occur, but no fertilization takes place.

What is gametic isolation?

Interspecies hybrids are viable and fertile, but subsequent generations have genetic abnormalities.

What is hybrid breakdown?

what are morphological traits

physical traits

What are the 3 drawbacks to reproductive isolation

1. Difficult to determine if two populations are reproductively isolated in

nature

2. Cases in which two different species can interbreed in nature yet

consistently maintain themselves as separate species

3. Cannot be applied to asexual and extinct species

▪ DNA sequences of

genes

▪ Gene order along

chromosomes

▪ Chromosome

structure

▪ Chromosome number

Which common set of characteristic is this

Molecular

Habitat

▪ lives on ground vs lives

in trees

▪ different temperatures

or climates

▪ different pH they can

tolerate

What common set of characteristic is this

Ecological factors

- fossil record

- DNA sequences

What common set of characteristic is this

Evolutionary Relationships

way of defining the concept of a species, an approach to distinguish one species from another

species concept

a species is a group of individuals whose members have the potential to interbreed and produced viable, fertile offspring

biological species concept

what is the consequence of general lineage concept

it forms an independent group of organisms with a particular set of characteristics

what are the to categories of reproductive isolating mechanisms

1. prezygotic

2. postzygotic

what is interspecies hybrid

an offspring produced by 2 species

what tends to be less common in nature, postzygotic or prezygotic isolating mechanisms

postzygotic

Interspecies hybrids are viable and fertile

▪ But subsequent generations harbour genetic abnormalities that are detrimenta

hybrid breakdown

▪ Occurs when members of a species that initially occupy the same

habitat within the same range diverge into two or more different

species

▪ Tends to involve abrupt genetic changes that quickly lead to the

reproductive isolation of a group of individuals

▪ Or changes→ ability to occupy new niche within geographic range of

current species

sympatric speciation

true or false - the pace of speciation is constant throughout the history of Earth

false