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APES Unit 3: Evolution and Biodiversity
Terms in this set (49)
a group of similar organisms that can freely breed with one another and produce fertile offspring
a group of individuals of one species that live in the same area
all the different species that live in the same area
a biological community of interacting organisms and their physical environment
Earth's Four Scientific Principles of Sustainability
1. Reliance on solar energy
2. Nutrient cycling
3. Population control
the number of different species in an area
comparison of the relative abundance of each of the different species
change over time, process by which traits that enhance survival and reproduction are passed on more frequently to future generations of organisms than traits that do not, thus altering the genetic makeup of populations through time
Where all of Earth's biodiversity came from.
Process of evolution through natural selection
1. Some individuals in a population possess certain inherited characteristics
2. These individuals produce more surviving offspring than do individuals lacking these inherited characteristics
3. As a result, the population gradually has more and more individuals with the advantageous characteristics (adaptations).
4. The population evolves over generations.
Examples of natural selection
Industrial Melanism in Peppered Moths.
DDT resistance in insects.
Speciation by natural selection
Natural Selection can lead to speciation (formation of new species)
Competition for scarce resources leads to specialization
Over time one species may evolve into several species with different adaptations & niches → this results in reduced competition, sharing of limited resources
Speciation by allopatric speciation
species formation due to physical separation of populations
- also called geographic isolation
- Can be separated by glaciers, rivers, mountains
Archipelagos and mountain ranges
Darwin finches of the Galapagos Islands
Arctic fox and gray fox
Mechanism of speciation. The accumulation of changes in the frequency of alleles (versions of a gene) over time due to changes that occur by chance.
Mechanism of speciation. movement of genes from one population to another. Ex: flowering plants (genes move by pollinators, wind), seeds (dispersal methods)
Mechanism of speciation.
Self-fertilisation (ex: flowers).
Assortative mating (phenotypically similar individuals mate)
Artificial selection (dog breeding, crop plants, GMO's)
Genetically Modified Organisms
GMO's use recombinant DNA.
Genes or portions of genes from different organisms.
Natural selection operates in 3 ways
Stabilising selection - most common form. Ex: human babies born too low or high in weight have difficulty with survival.
Directional selection - Ex: Peppered moth.
Disruptive Selection - Ex: Darwin's finches with small and large beaks.
Postzygotic reproductive isolation
Parents can form a zygote together, but the offspring cannot reproduce. Also pairing of species that will always lead to miscarriages.
Prezygotic reproductive isolation
Isolation happened between groups of the same species before an egg was even fertilised. For example, behavioural changes. Can also be geographic, for example populations being separated by great distances.
When one species diverges into two species because of geographic isolation since conditions could be different. Galapagos finches, arctic fox and gray fox.
Habitat alteration causes greatest biodiversity loss
Urbanization and suburban sprawl
A few species (i.e. pigeons, rats) benefit from changing habitats
Theory of Island Biogeography
Used to assess the impacts of habitat fragmentation on populations.
First introduced by Robert MacArthur, an ecologist, and EO Wilson, a biologist.
Used to explain how island species are distributed geographically. This explains how the species have emerged as a result from a balance of those added by immigration and removed from extirpation. Additionally, the theory delves into how information from the island, such as its size and distance from the mainland, can explain species richness.
Fewer species colonize an island far from the mainland.
Large islands have higher immigration rates.
Large islands have lower extinction rates.
How does the theory of island biogeography relate to fragmentation of land on the continents?
They are related because the theory provides a model for how much habitat fragmentation occurs and the amount of life a fragmented habitat can support.
Forests are fragmented by roads and logging
Small & isolated forest fragments lose diversity fastest
Largest species lost first
Fragmentation is one of the prime threats to biodiversity
The condition in which, at ecosystem boundaries, there is greater species diversity and biological density than there is in the heart of ecological communities.
Essentially makes the fragmented forest than it already was.
Causes of variability:
How old the habitat edges are
Drastic weather events
The structure of vegetation
Increase in animal populations
The sizes of fragments
The season in which it is occurring
Other edges nearby
Natural transition area between two ecosystems. Has been there overtime and has different species in it than you would in the other areas around it.
Speciation by Sympatric Speciation
Less common than allopatric speciation.
Species form from populations that become reproductively isolated within the same area.
Feed in different areas, mate in different seasons.
Hybridisation between two species.
Show relationships among species, groups, genes, etc.
Scientists use these to trace how certain traits evolved.
When faced with an environmental change, a population of species
Origin of Earth
4.5 billion years ago
Evidence of life (prokaryotes) - 3.5 bya
The Cambrian explosion (most major groups of complex animals appear) - 530 mya
Quaternary - 190,000 ya - first humans
Organisms that first appeared on Earth
Single-celled prokaryotes -> single-celled eukaryotes -> multicellular eukaryotes
Temperate and polar latitudes
Variable climate favors fewer species, and species that are widespread generalists
Greater solar energy, heat, and humidity promote more plant growth to support more organisms. Stable climate favors specialist species. Together these encourage greater diversity of species.
What types of species are more prone to extinction?
Endemic, specialists, generalists.
3 levels of biodiversity
1. Ecosystem diversity = the number and variety of ecosystems.
Rapid vegetation change and varying landscapes within an ecosystem promote higher levels of biodiversity.
Example: tropical rainforest
2. Species diversity. Estimated 3-100m species on Earth.
3. Genetic diversity within a population.
Populations with higher genetic diversity can survive.
Populations with low genetic diversity are vulnerable.
Locally (=extirpation) - a species is no longer found in an area it once inhabited but is still found elsewhere in the world.
Ecologically - occurs when so few members of a species are left they no longer play its ecological role.
Globally or biologically (= extinction) species is no longer found on earth.
Five mass extinctions
In the past 440 million years, mass extinctions have eliminated at least 50% of all species
After every mass extinction, biodiversity returned to or exceeded original state.
Current mass extinction
We may lose more than half of all species.
Current global extinction rate is 100-1000 times greater than background rate.
What makes a species vulnerable to extinction?
Low reproductive rate (blue whale, giant panda, rhino)
Specialised niche (blue whale, giant panda, everglades kite)
Narrow distribution (many island species, elephant seal)
Feeds at high tropic levels (bengal tiger, bald eagle, grizzly bear)
Fixed migratory patterns (blue whale, whooping crane, sea turtles)
Rare (many island species, african violet)
Large territories (snow leopard, tiger, elephant)
Free ecosystem services!
Provides food, shelter, fuel, medicine
Purifies air and water, and detoxifies wastes
Stabilizes climate, moderates floods, droughts, wind, temperature
Generates and renews soil fertility and cycles nutrients
Pollinates plants and controls pests and disease
Maintains genetic resources
Provides cultural and aesthetic benefits
Humans feel connected to nature = biophilia
Allows us to adapt to change
IUCN Red List
The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world's threatened species.
(human) P-population growth
Characteristics of successful invasive species
High reproductive rate (r-selected species)
High dispersal rate
High genetic variability
Characteristics of Ecosystems Vulnerable to Invasive Species
Climate similar to habitat of invader
Absence of predators on invading species
Early successional systems
Low diversity of native species
Absence of fire
Disturbed by human activities
1975 Convention on International Trade of Endangered Species
Important international agreement
Signed by 169 countries
Lists 900 endangered species that cannot be commercially traded
Restricts trade of 5000 animal species and 28,000 plant species at risk
Endangered Species Act (1973)
forbids government & private citizens from taking actions that destroy endangered species or their habitats
-To prevent extinction
-Stabilize declining populations
-Enable populations to recover
-NMFS and USFWS→ IDs, lists, and prepares recovery plan
Currently, the U.S. had 1,363 species listed as endangered or threatened.
Hotspots of biodiversity
1) It must have at least 1,500 vascular plants as endemics — which is to say, it must have a high percentage of plant life found nowhere else on the planet. A hotspot, in other words, is irreplaceable.
2) It must have 30% or less of its original natural vegetation. In other words, it must be threatened.
What can we do to protect biodiversity?
1. Immediate action to preserve world's biological hotspots.
2. Keep intact remaining old growth forest.
3. Complete mapping of world's biodiversity for inventory and decision making.
4. Determine world's marine hotspots and assign priority for action.
5. Concentrate on protecting and restoring lake and river systems (most threatened ecosystems).
6. Ensure inclusion of full range of ecosystems in global conservation strategy.
7. Make conservation profitable.
8. Initiate ecological restoration projects worldwide.
Whether several small reserves are superior to one large reserve in regards to conserving species richness and diversity in a habitat that is fragmented. The amount of space a species has access to has an impact on its ability to live successfully.
It is a connection of two wildlife habitats with another similar wildlife habitat. Allows for animals to move across land and promote migration. They help promote diversity and also make up for habitat fragmentation.
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