3B2 Relationships and Classification of Organisms Flashcards
Explore how classification uses cladograms and phylogenetic trees to show relationships and unique traits among organisms.
What is an organism?
A living entity that grows, reproduces, and responds to stimuli.
Organisms can range from single-celled organisms, like bacteria, to multicellular organisms, like plants and animals.
True or False:
Only animals are considered organisms.
False
Organisms belong to various kingdoms of life, not just the animal kingdom.
Define:
Cladogram
A diagram showing species relationships through shared traits.
Cladograms display evolutionary connections but do not indicate the timeline or genetic distances between species.
What is a phylogenetic tree?
A diagram showing evolutionary relationships with branch lengths.
Phylogenetic trees illustrate evolutionary time or genetic changes, offering more detailed information than cladograms.
What does each node in a cladogram represent?
A common ancestor shared by species.
Nodes mark points where species diverged, indicating shared evolutionary history.
True or False:
Cladograms show the exact time species diverged.
False
Cladograms depict relationships but lack information about divergence timing.
Fill in the blank:
In a phylogenetic tree, the ________ represent descendants of a common ancestor.
branches
Branches connect nodes to terminal species, outlining evolutionary paths.
What is a sister group in phylogenetics?
Two groups sharing an immediate common ancestor.
Sister groups are closely related, forming each other’s closest relatives.
What is the principle of parsimony in cladistics?
The simplest explanation is preferred.
Parsimony reduces assumptions by selecting hypotheses with the fewest evolutionary changes.
True or False:
Phylogenetic trees are hypotheses.
True
They represent evolutionary relationships based on available data and can change with new evidence.
What data is used for phylogenetic trees?
Morphological and molecular data.
Common examples include physical characteristics, DNA sequences, and protein structures.
How are outgroups used in phylogenetics?
To root the tree.
Outgroups help determine ancestral traits by providing a reference point outside the main group.
Fill in the blank:
A _________ group includes a common ancestor and some descendants.
paraphyletic
Paraphyletic groups exclude certain descendants, unlike true clades.
What is homology?
Similarity due to shared ancestry.
Homology in biology refers to the existence of shared ancestry between a pair of structures, or genes, in different taxa.
Why are phylogenetic trees important?
They show evolutionary relationships.
Trees help study biodiversity, trace traits, and inform conservation and taxonomy.
Fill in the blank:
_________ _______ refers to traits that evolved independently in different lineages.
Convergent evolution
Examples include the wings of bats and birds, which evolved separately for flight.
What is a polytomy?
A node with multiple branches.
Polytomies indicate unresolved relationships, often due to limited or conflicting data.
True or False:
Cladograms and phylogenetic trees always have the same topology.
False
Cladograms emphasize relationships, while phylogenetic trees include timing and genetic distances.
What are prokaryotes?
Organisms without a nucleus.
Prokaryotes include bacteria and archaea, characterized by their simple cell structure lacking membrane-bound organelles.
What is the genetic material in prokaryotes?
A single circular DNA molecule.
Prokaryotic DNA is located in the nucleoid region, not enclosed within a nucleus.
How do prokaryotes reproduce?
By binary fission.
Binary fission is an asexual process where a prokaryotic cell divides into two genetically identical cells.
What characteristic defines animals as a group?
Multicellular organisms that are heterotrophic.
Animals consume organic material for energy and lack cell walls, unlike plants and fungi.
True or False:
All animals have a backbone.
False
The majority of animal species are invertebrates, which do not have a backbone. Invertebrates include insects, mollusks, and arthropods.
Fill in the blank:
Animals store energy as _______.
glycogen
Glycogen is a polysaccharide that animals use for energy storage. It is primarily stored in the liver and muscle cells and is broken down when the body needs quick energy.
What is the primary mechanism for plants to get energy?
Photosynthesis
Plants use sunlight, carbon dioxide, and water to produce glucose and oxygen, a process driven by chlorophyll in chloroplasts.
What type of cell wall do plants have?
A cell wall made of cellulose.
Cellulose provides structural support, helping plants maintain their shape and resist external pressures.
What characteristic defines fungi as a group?
Eukaryotic organisms with a cell wall made of chitin.
Fungi are heterotrophic, acquiring nutrients by decomposing organic matter.
True or False:
Fungi are autotrophic.
False
Fungi lack chlorophyll and cannot perform photosynthesis, relying on external organic matter for nutrients.
What characteristic defines protists as a group?
Diverse eukaryotic organisms that are not plants, animals, or fungi.
Protists can be unicellular or multicellular, autotrophic or heterotrophic, and inhabit diverse environments.
True or False:
All protists are microscopic.
False
Some protists, like kelp, are multicellular and can grow up to several meters long.
Fill in the blank:
Protists that move using pseudopodia are called _______.
amoebas
Amoebas extend their cytoplasm to form pseudopodia, which aid in movement and capturing food.
